"No!" screamed Merryn, her face pale, eyes wide as the goop engulfed both of them. As the sludge spread up his torso, Stan let out a bellowing roar and the front ranks of the horde stuttered into motion, crowding forward to meet the two forms facing them.

As the first of the zombies stepped into the sludge, it spread, freezing anything it touched. A silver grey stain spread like lightning through the ranks of the undead, quicksilver lacing through the horde, moving back through the still marching deadheads, shifting like mercury through them until everything went still.

"Take us down!" screamed Merryn.

"I can't, not yet," shouted Rob. "We have to be patient, Merryn."

"Then take us closer damn it, I need to see Hope, I need..." tears were running down her face as Rob brought the 'copter down to near ground level behind the still forms of Hope and Stan. Both stood, with arms outstretched, still touching the grasping hands of the few walkers who had reached them first. Both were covered head to foot in a shining translucent cocoon of silver grey.

Both were still.

For several long minutes, Rob kept them at a safe distance, then he dropped the 'coptor to the ground and stilled the engine.

As soon as she was able, Merryn was out of the cockpit and sprinting towards Hope. She ignored the shouts of the others as they struggled to get out of their seats, ignored Rob's voice over the speaker ordering her to return. 

And then she was at Hope's side.

Hope's face was coated in a skein of translucent shining silver, and was serene, a faint smile hovering on her lips in stark contrast to the slack grey face of the walker who had touched her outstretched hand.

Merryn slumped to the ground, her legs weak, and cried, sobs shaking her body as she sat. It wasn't until a few minutes later that she became aware of the others. Eddie had knelt down next to her and had pulled her into a hug, and Tom and Andrew stood close by looking helpless, facing the wall of unmoving undead that stretched away from them on either side.

Nothing moved.

"I knew you wouldn't take this idea well," croaked a voice.

"What the actual..." began Andrew, his jaw dropping. There was a faint ripping noise and Hope's hand moved upwards to pull the gossamer-thin cobweb of dried sludge from her hair. "This stuff's disgusting."

"Wait!" she commanded as Merryn leapt to her feet. "It may not be safe."

They watched as Hope divested herself of the remaining grey material, then proceeded to help Stan from his coverings.

It was only then the two of them moved away from the still frozen walkers and Hope allowed herself to be enveloped in a teary hug.

"Would you folks mind if we moved a little bit away from the deadheads?" asked Rob after a few moments. "All these zombies standing there looking at us are making me a little nervous, and I'd like to make sure the helicopter is out of range, just in case we need it."

Merryn turned to face the pilot, and nodded, drawing herself back together as he watched. "Drop the 'copter at the other end of the site Rob, somewhere where you have a clear view of things. We'll come across to you. I need to have a walk to clear my head."

Rob nodded, and soon Rescue 1 lifted back into the sky, its speakers as silent as the horde it left behind.

"I need a shower," said Hope. She looked around at her friends; Merryn, Eddie, Andrew, and Tom. Stan stood to one side, silent and unmoving once more.

Hope took Merryn's hand. "I'm sorry I couldn't let you know what was going on. I knew you'd object. I asked Rob to take you and the others away from the area so I knew you'd be safe. I was pretty certain what we were going to do would work, but I wanted to be sure the people I cared about were out of harm's way."

Merryn nodded, unable to speak.

Hope let go of her hand and linked arms with her as they walked towards the helicopter, the others staying close so they could hear what she was saying. Andrew and Eddie held hands as they walked alongside.

"After Stan and I were sent to the Isle, I was a little lost for a while, but Command was kind enough to keep me in the loop on things. I had regular chats with Mal, and Captain Summers checked in sometimes too. When you and Andrew encountered the goop, it got me thinking about things and I started talking to some of the scientists on the Isle about what they knew, and what they'd discovered from Stan and my samples. Then one of the scouts up there found another car with goop in it. This time it wasn't too far from the Isle, a car parked in a garage in Portsmouth, and from the photos and information we found in the house we think it was a couple of older women, sisters, who lived together.

"We weren't quite sure what to do with it at first other than monitor it until we heard the reports of what happened at the power station on the north coast." Hope tugged on Merryn's arm, her eyes shining with excitement. "Electricity was the key. The engineers on the Isle built an electrified cage around the car. That put the goop into stasis, in the same way as the electrified fences did for the thousands of walkers at the power station. Once the sludge was rendered frozen they picked up the whole car, cage and all, and it was transported with great care to one of the old Victorian sea forts to the east of the Isle of Wight. What was once built to keep the French at bay by the Victorians became an isolation laboratory, one that housed the goop, a few zombies collected for testing, and of course myself and Stan."

Hope caught a dark look from Merryn but continued. "We volunteered, don't worry. I discussed everything with Stan first, and he wanted to try and help in any way he could. As did I, and finally my own medical training came into play too.

"The goop was the key to it in the end. As you and Eddie saw in the field Merryn, it connects the walkers, and it does so by infecting them with a new variant of the virus. The goop is not sentient as such, but it is alive in the same way a virus is alive: it spreads. But this variant needed a catalyst. In the case of the swarm on the dual carriageway that you witnessed with Eddie, the catalyst was the lone zombie who had walked into the goop when it had spilled out from its prison: the people carrier hit by the tree branch. The one zombie who wandered into it gave the patch of sludge the key it could use to infect the swarm when it came into contact with it, and then connect them as a super swarm, one that moved with intent, like a swarm of bees or flocking birds.

"The question then was how could we utilise our little bucket of goop we found in the car to help us.

"The first step was to try using a different catalyst, me. So we popped a lone zombie into a secure room, added some sludge, and then I joined it. It didn't work. But what it did do was make the zombie who was in the room with me aware of my presence. As soon as I came into contact with the goop, the zombie sensed me and attacked me. Stan was on the other side of the secure door watching. He broke in as I was defending myself and intervened, holding back the zombie who was trying to bite me. As he did so, he trod in the test patch of sludge too and we witnessed a similar reaction to what you've just seen here. Only the goop, myself, and Stan, three different variants acting in concert could stop the walker.

"We learned several things in the first experiments. When the catalysts, Stan and I, came into contact the goop got used up. That's what a catalyst does, it helps the reaction happen but doesn't get used up in the process, which is a good job, or Stan and I wouldn't be here talking to you now."

"Stan ain't saying too much at this point," noted Andrew. "You okay big man?"

Stan gave a slow nod.

"Well that's something," said Andrew. "May I ask a question?"

"Of course," said Hope.

"Why were you smiling? When we thought you were dead, and you were covered in that shiny stuff, you were smiling. I wondered why."

"Well," said Hope. "That's something else we learned. Although the goop wasn't sentient as such, it did store some semblance of the people who had formed it. We couldn't communicate with it in as direct a fashion as we do with Stan, but it had some idea of what we were doing. And, when we utilised the first bucket of goop in testing, I picked up a sense of tremendous approval and happiness that they'd been able to help us fight back against the walkers. I asked Stan and he said he felt it too. It was like they'd been waiting for some way to help and when we turned up, we gave them a reason to get involved."

"So, scientific logic would demand you try to replicate the process," said Eddie. "Make sure your hypothesis was correct."

Hope nodded. "We tried it again the following week. The same scout found another batch of goop, this time in a caravan, and this time we tried it on a larger group of deadheads, twenty, in the field. And it worked again, the goop multiplying and spreading as more zombies were present. But again, once the deadheads there were deactivated, the goop was rendered inert.

"Since then, we've had all the scouts from the Isle out scouting for more goop, to ensure we had the capability to try and tackle a larger group of walkers if we needed it. Last week a different scout found another patch of sludge in an old people's home, a team was sent in, and using the electrical cage method we once again managed to secure it, ready for use in case we needed it. Tom and Andrew also found some more goop on their trip up to the power station but we haven't had a chance to secure that yet.

"So, when the Cruiser reported in this swarm that was taking Cardiff apart, we realised we had little choice but to test out our method on a full swarm as we were running out of time. That was the risk this time, that the sheer size of the swarm would overwhelm us and our bucket of goop."

Hope looked over at Andrew. "And to answer your question, the reason I was smiling today was that the relict memories of a family of six who formed our bucket of goop today filled me as I touched that first walker. Memories of love, a certain craziness, laughter, positivity, and a determination to succeed pulsed through both Stan and I as the goop spread through the swarm. That family saved us, and even though they're long gone as individual humans, they still helped us fight. And they were proud of that somehow."

"And what would have happened if you had not been successful?" asked Eddie as they reached the helicopter.

"I would have radioed through to Command and ordered an airstrike," said Rob. "That was my other job today, I was the insurance policy."

"And you would have taken out Stan and Hope in the process," said Tom.

"That would have been my request," said Hope looking over at him. "We are fighting a war, Tom, sometimes sacrifices have to be made, we have to function on logic and calculated risk. Today our calculated risk seems to have worked."

"It's good to have you back with us," said Eddie. "You and Stan."

Andrew turned and pointed back to the unmoving swarm. "So, what do we do about that?"

"Nothing," said Hope. "They will degrade over time. All we can do is say a few words for the finally dead and leave them to it." She turned to the pilot. "I need a shower. Could we get back to the power station?"

Rob nodded. "That is a damn fine idea. We need a little time to process what just happened, have a good cuppa, and sit behind a nice strong fence." He pointed at the stationary pile of walkers. "That is giving me the creeps and I'll be much happier when I don't have to look at it anymore. I'll radio the Cruiser and let them know."