They parked in a dark side street then they fixed helmets; incongruous on a Welsh street. Armed with guns and the case, they rounded a corner and saw oil lamps in two windows of a large detached house. Sneaking up the path, Jena hesitated and tugged at Abdul to stop. They couldn't just open it on the doorstep and ring the bell, risking the householder stumbling on the case or taking it in.

Jena whispered. "There's a low hedge near the door." She opened the case on the side of the hedge away from the door and waited for a few minutes for the blue blocks to emit particles.

"To think this might be the start of a diffusion of more sanity for the planet or the acceleration to the end," Abdul said. "I hope they don't notice the blue fluorescence."

"If they look as if they're going to touch it, we'll have to point our guns at them and tell them to go in the house while we run off with the case. Right, who's going to play Trick-or-Treat?"

"Isn't it Knock-and-Run? Although, we're only hiding, and we are giving them a treat," said Abdul. "All right, I'll do it."

Jena suppressed a laugh at the ludicrous vision of a NASA spaceman in full suit sneaking up to a door, knocking on its letterbox, and running back to her in the bushes.

"You could have just lobbed a stone at the door, you muffin."

"Now you tell me."

A moment later, the door opened and an angry, elderly man in a dressing gown stepped out on the path. "Who's there? I bet it's young Robbie, ain't it?"

A woman in her thirties came out. "Come on, Daddy, it's cold out there." She joined him on the path, put an arm around him, and together they returned to the house and shut the door.

"I'll count that as a success," Jena said, as they retrieved the case and turned out of the gate. Across the road, The Glyndwr Arms released sounds of talking. Dim lights escaped through curtains from hurricane lamps.

They peered in through gaps in the curtains. Abdul said, "Four-no, five men and two women. They're having drinks as if nothing has happened."

"Probably a bit like that father and daughter back there. She's lost twenty years, called the crotchety old feller, Daddy, and cuddled him like a young girl might. Are we up for it? Seven birds with one stone?"

"I'll hold the case open while you point both hand guns, although the sight of us might freak them into a catatonic trance."

"Shall we ask Ryder first?" Jena said.

"He'd refuse permission."

"We could ask, let him refuse us, and do it anyway. It would really piss him off," she said, grinning behind her visor.

"I thought you liked him."

"So?"

They burst through the double doors and stood there facing the drinkers. Most were senior citizens with slow reactions. A middle-aged man about to sip from a bottle hesitated as if frozen. Abdul put the case on a stool and opened it. The six blue bricks shimmered. The drinkers' eyes flitted between the mesmerising contents of the case, the astronauts' space suits, and Jena's guns. One of the men let his bottle slip out of his shaking fingers. It smashed on the floor sending a jet of liquid shooting back up. Jena took pleasure from the beautiful application of Newton's Third Law of Motion: for every bottle of beer hitting the floor, there is an equal and opposite fountain of beer rocketing up.

Jena spoke, her American accent adding another oddity to the occasion for the drinkers. "You will find your memory loss will stop, and you'll start remembering things from now on. Breathe on others, spread it around. When we leave, lock the door for at least half an hour."

Abdul closed the case and said in his equally strange Qatar accent, "We'd buy you a round, but we haven't any money. Have a drink anyway."

They ran to their car. In between bursts of relief laughter, Jena warmed with the thought they might have done some real good. But then she remembered the aliens were responsible for both cases. Had she been an unwitting accomplice by implementing an awful plan?

SATURDAY 10 OCTOBER 2015, 03:00 HOURS, AFTER ABANDONING ANAFON.

Both vehicles hid behind a low hill while Ryder trained night-sight binoculars at Menai Bridge. They had seen no one on the way, not even candlelight in windows. RAF Valley was on the island of Anglesey across 300 metres of grey Irish Sea slopping back and forth up the Menai Straits. Beautiful in the moonlight following an earlier rain, the suspension bridge glistened metallic green. Nineteenth century graceful catena curves and vertical steel ropes tried hard to sooth the troubled minds looking out for trouble.

"I don't like it," said Ryder. "There's a barbed-wire barricade at this end. Okay, we have bolt-cutters, but I can't see the other end of the bridge. Abdul?"

"I see obstacles on the bridge but no more than the surprising amount of debris on the road all the way here. It's too dark, and the curve in the surface of the suspension bridge stops us seeing the end."

Ryder remembered something. "There's another bridge. Britannia was road and rail but used only for the railway for years."

"Let's have another look at that map. Yes, the railway goes all the way into the airfield."

"No," Ryder said, "we can't drive on the tracks. The wheelbases on our vehicles are wider than the 4-feet-8.5 inch-railway gauge, so we'd be driving over the sleepers. It would be a hell of a drive."

"I'm up for it. Both vehicles have excellent suspension. The pickup in particular can have the wheels dive into holes without the chassis deviating."

"Abdul, we have delicate computers on board and the case."

"Ryder, the computers and case are tough enough. Are you?"

"You think it would be a soft option to go across this bridge and stay on the roads?" Ryder checked his anger with Abdul. He found that lately he was apt to boil over too easily. The deaths and increasing danger must be getting to him. "Let's have that map. Maybe you have a point. The railway hardly touches any villages."

Ryder smiled as he could tell that Abdul had sensed a rare point win over him.

Abdul said, "We could put it to a vote."

"No need, Abdul. We don't want them to think we aren't decisive, do we?"

A LARGE PADLOCK LOOKED AT THEM. Gustav wielded his favourite toy. The turbo-assisted, long-handled bolt cutter was eager to get to work, and even with the caveat of Ryder's shushing, the heavy-duty padlock had its steel U-shaped shaft sliced. A sharp crack echoed off nearby grassy banks, but Jena caught the steel debris in her hands to prevent further noise.

"Well caught," Gustav said. "Now squirt the lubricant on the hinges and we're in."

Ryder and Abdul patrolled with loaded rifles and night sights during the operation to allow the vehicles onto the tracks. Soon they were all aboard. They had opted to straddle one rail. Ryder drove the pickup and struggled, losing his fight with the wheel. Gustav drove the estate car and pulled away in front of him. In spite of the relative security of not driving on the roads, they agreed on using sidelights rather than headlights that might have attracted more than moths.

Teresa sat next to Ryder, with Abdul in the seat behind, along with Megan. Bronwyn rode for the extra comfort in the estate car with Jena and Gustav.

"Ryder, you would find driving a lot easier if you drove faster," Teresa said. "Look at Gustav, he's leaving you for dust."

"It's not a race."

"Granted, but a bit more speed would allow the wheels to skip over the smaller gaps in the ballast between the sleepers. For God's sake, try it, man."

To his surprise, the pickup did ride with less walloping at a speed of thirty, as opposed to twenty, but it still rocked around, creating worrying banging and crashing noises in the rear.

Jena's voice came over the phone. "Ryder, you haven't engaged the turbo-assist suspension, have you?"

"What's she talking about?" He glanced at the eerie back-lit green dashboard.

"And I thought you two were entwined in thought and deed," Teresa said.

"Funny. Hey, you drive this contraption more than me."

"It's this lever, but it's engaged so I don't know why it isn't working. Any ideas back there, Megan?"

Megan undid her seatbelt and leaned forward between them. "Gotta have four-wheel drive on," she said, sat back and put her headphones back on.

The pickup lifted and sailed across the sleepers.

"Hey, I'm impressed with this suspension," Ryder said. "Why did no one tell me this before? It would have made cross-country driving in the Anafon Valley so much easier."

"Figures," Teresa said. "You don't ask for any advice in case they think you're as weak as I know you really are."

"Come on, Teresa, we've been falling out over trivia for over a year. You can't blame Jena for that."

"She's just a bitch-on-heat that happened to be in front of you at the right time."

Ryder was about to reply when Jena came on the phone. "This bitch thought you ought to know we're coming up to the bridge and stopping for a reccy."

"Was your phone on all that time?"

Teresa played with it. "So?"

"THIS IS GOING TO BE SPOOKY," Megan said. "Do we have to drive underneath the road bridge? It'd be like in a tunnel."

"That's where the railway lines go," Ryder said, looking through his binoculars at the double-decker bridge and not seeing any sign of movement on the road above or lines beneath. Both, however, were barricaded with gates and rubble.

"Do you think the Anglesey islanders were trying to stop ARIA-infected people crossing?" Abdul said.

Ryder talked as he peered through the eyepieces. "It might have slowed ARIA by a day or two, but the ferry from Ireland would have been disgorging infected people unless they also laid a minefield out at sea."

Gustav had his own field glasses. "In our favour is that no motorised traffic has passed for months."

"No, they'd still be on the island," Jena said. "Some would boat across the straits or clamber over those barricades."

"We could cross by sea, if we could find a boat," Abdul said.

"Probably quicker to make a dent in that heap of rubble than winch ourselves over it. Pity we daren't use explosives," Ryder said.

Gustav stood on the pickup's bonnet. "I can see where we can hook the pickup's winch cable on a strut the other side of the rubble and take it over towing the estate car."

The women took up armed-guard duties while the men sorted the winch.

Gustav drove the pickup right up to the mound and released the winch reel at the front. Ryder and Abdul took the cable over the mound and hitched it over a bridge support. The winch rewound its cable while Gustav put the pickup into first gear and applied a gentle acceleration. Jena drove the towed estate car behind.

Ryder watched the taut cable and checked their cable connection round the strut. "It's too noisy."

"Sounds worse under here than out in the open," Abdul said, waving Gustav on towards him. "Look, it's nearly at the top. Doing well."

The pickup rounded the top and started down, putting a greater strain on the nylon towrope pulling the estate.

They stood around, looking pleased with themselves.

"Problem, people," Abdul said.

"Not another," Ryder said.

"Ryder, you know you said we weren't to use side lights while crossing the bridge in case we were seen from the island?"

"So?"

"I see the problem," Jena said, walking along the sleepers a few metres. "One of us needs to walk in front with a torch. There's a narrow surface a foot or so wider than the rails then planks."

"It's been only seven months since this was a busy mainline route, so as long as we take care, it should be all right." Ryder couldn't bear the thought of going back.

Gustav faced Ryder. "There's no way we can safely drive at thirty over this. A wheel might skid on a plank or break one."

Teresa brandished a flashlight. "I'll walk in front. There are no bends so you should see my torch."

Gustav followed her in the estate car at walking pace. Being unable to see the stars or moon overhead, along with the more rickety travelling, made the journey feel more hazardous than in the open.

Abdul phoned Ryder from the lead car. "Teresa says she can't see a mound at the other end but there is a gate. No big gaps in the driving surface so far."

Ryder's stomach lurched. The drive took on the gut-churning experience of a fairground ride-of-fear where the driver had no control over the direction, couldn't see very much, and could be spooked by the unexpected.

Ryder looked left and right. Even a single candle at night should have been seen miles away. In the mirror, he thought he saw a red light but realized it must be a reflection of his own rear lights.

"Look out!" Megan called.

Gustav must have braked. Even at just over walking pace, it took him too long to apply the pickup's brakes, so they collided with the estate car, making it lurch. Ryder jumped out and ran to the front, imagining Teresa lying in the road.

She was a few metres in front, waving her torch at a hole in the ground.

Gustav called out of his driver's window. "I know you want us to get there, but there's no need to push." He had a grin, as did everyone else: so pleased to see Ryder at fault for once.

Abdul laughed as he walked round to the rear of the pickup and pulled out a rectangular sheet of tough PVC used for off-roading, and placed it over the gap.

"And you can shut up," Ryder said to Teresa, who'd joined in the stress-relief merriment.

"You have to stop again," she said.

"Another hole?"

"The barrier in front. Looks like several large gates you see around building sites. They're chained together so shouldn't be difficult to get through."

Gustav cut through the chains, and they used the pickup to push the gates down. Ryder was afraid of the noise of crashing metal. People might wake and think there were vandals rampaging or a train crash, one of which was true.

Away from the bridge, Ryder could see the moon and stars once more. He tried not to think of the latent terror lurking in the silhouetted landscape flitting by. The demon-looking trees threw their branches menacingly. Gusts of westerly winds grabbed their leaves and hurled them into the air. Many splattered across the windscreen.

Ryder lifted his spirits where he could by absorbing the monochrome scenery. Megan sat beside him, Teresa in the back with Bronwyn. Jena joined the two astronauts in the estate.

Unlike the stomach-gripes he had driving on the road towards the Chester airfield, they drove in relative safety. Away from the trees, they had miles of mostly flat and undulating fields on either side, with an occasional sight of the ocean on their left.

Teresa's phone beeped. "Hey, I hope you two aren't quarrelling back there." Ryder heard Jena laughing.