The Doctor ran back to the TARDIS through the woods. He hurried into the sickbay first to check that Josh was still there. He was. He was sitting on the bed watching a film of some kind on the sickbay monitor. The Doctor put the egg down on the adjacent bed. "Change of plan," the Doctor informed the teenager as he looked at him curious. "There are too many of them, far too many of them, over too big an area for me to blow the tunnels to trap them," he recounted his discovery.

"How many are there?"

"I don't know, but they're not just in one area of the caves, they are spread out a lot further than I thought." The Doctor stared at the egg on the bed trying to think of a way to keep them underground. He mussed his hair with his fingertips. His headache should have begun to subside by now, but no, it was still lingering slowing his thoughts. "Sonic!" he exclaimed. "Big eggs, big sonic," he stated. "If I create a sonic beacon to emit a regular sonic pulse?" he thought out loud. "That should keep them underground, or, drive them out of the area completely? Let's go for underground," he confirmed. "That will do for now, until they learn it's harmless, hopefully they're not too smart too quickly," the Doctor stated. "I'll be back."

"Is that an egg?"

"They're breeding," the Doctor confirmed.

"And they lay eggs? Dogs don't lay eggs."

"They're definitely not dogs. They're alien," the Doctor informed Josh. "I need to find out where they are from so I can try and get them back there, but I need to sort out the sonic beacon first."

"What about the bats?" Josh asked him.

"Bats?"

"There are bats in the woods. They're protected you're not allowed to harm them," Josh informed the Doctor. "Won't a sonic beacon hurt them as well as the creatures?"

"It'll be a different frequency," the Doctor responded. "I'll be back soon, I promise."

"People only promise things like that when they don't know if they're going to be."

"I will be," the Doctor insisted. "But, I've got to go and do this."

"Because it's your job?"

"Yes."

"Kind of, right?"

"Yes."

The Doctor turned to leave the sickbay. "Whoa, Mister? Your back is bleeding again. I mean properly bleeding. Your T-shirt is soaked."

"I'll change it when I get back," the Doctor told him.

"But…"

"Just hang tight," the Doctor suggested. "Finish watching your film. I'm not going to be long."

The Doctor headed to his workshop and gathered what he needed to make a powerful sonic beacon. It would emit a broad wave high pitched sonic boom every twenty seconds. It would disrupt anything that was sensitive to sound at the selected frequencies. He wasn't sure what it would do to any local bat colonies, his aim was to keep the murderous alien carnivores underground and stop them slaughtering any one unlucky enough to be passing by. He couldn't afford to think about the bats.

All of this was going on and Josh was worried about the bats. Hopefully all it would do was keep them in their roosts, but then, I bats started flying round disorientated and confused, raining down onto the forest floor as they bounced haphazardly off trees then Josh would know that he'd lied. The Doctor used the sonic screwdriver to check the boom created by the beacon. He took a further four minutes to increase the frequency and eliminate those that bats utilised. They would be fine.

He couldn't afford to waste any more time, it was mid-June and the sun was beginning to come up. He'd been at it all night, and Josh had been awake all night. He needed to get back and get them something to eat and then encourage the boy to get some sleep.

The Doctor shouldered the beacon and ran out of the TARDIS. He headed back down to the entrance to the storm drain, but rather than go into it, he went up over it and continued into the woods. He headed toward the boundary of the old estate and toward the abandoned slaughterhouse. When he estimated that he was half way there he searched for a suitable location to position the sonic beacon. He'd prefer it to be in as clear a spot as he could get it so it could broadcast freely. Brambles and vines choked the forest floor. He clambered up a tree and hung the beacon from a branch six metres above the ground. He jumped down, ignoring his back as it protested the skin splitting jolt as he landed, and checked the beacon was working with sonic.

Hurrying through the trees toward the estate boundary the Doctor measured the impact of the beacon. It was powerful enough. He made it to the drain he'd escaped from into the concrete creek bed next to the abandoned slaughterhouse. His sonic beacon was still registering at 95% of the power he registered directly under the device.

He thought that he should check the other areas to make sure it remained strong as well, but as he was about to jump down into the dry creek he heard a bang. It sounded like a vehicle door slamming. Not a car, bigger than a car. He ducked down into the undergrowth.

There was a truck parked on the tarmac by the slaughterhouse. It was a tall white truck with no logo and a rolling rear shutter. One brutish looking man had jumped out of the passenger side of the truck. He had a rifle slung over his shoulder, but he took it down and pointed it loosely toward the drain in the creek as he cautiously moved to the edge of the slope and looked down.

"It's clear!" the man called up to the driver and began to wave him backward. The truck was reversed so it was at the edge of the carpark. The driver jumped out. He also had a weapon, but rather than a rifle the Doctor thought it looked like a shotgun. He wasn't very good at identifying guns. He didn't like guns, and, he really didn't like what he was seeing. The two men unlocked the back of the truck and rolled up the rear shutter. There was another man in the back of the truck and he secured the shutter up. The driver with the shotgun clambered up into the back of the truck while the passenger kept watch with the rifle.

The two men in the back of the truck grabbed a butchered animal carcass. They tossed it down onto the slope and it rolled and bounced down into the bottom of the creek to land just outside the entrance to the storm drain.

"Still no sign of them," the passenger called out. The Doctor watched from out of sight as nine waste carcasses were tossed down into the creek. They were feeding them. They were getting rid of animal waste and feeding it to the creatures.

"They'll be along soon enough with this lot," the driver commented. "That's the last one." They tossed a final carcass down.

"I heard they got a homeless guy," the man who had been in the back of the truck stated.

"Yeah, heard that too," the driver agreed. "Something wrong with this last lot. They're bigger, meaner, I think they're mad or something."

"All the better for us," the passenger called over to them. "They're normally out by now."

"What have we got for them tomorrow?" the driver asked.

"Pigs tomorrow. A good bit of pork. A whole herd to be culled because of swine flu. Makes it much more expensive to dispose of them safely," the man out the back of the truck commented and laughed. "Make sure you got your infection control kits with you on pick up. Make it look good, yeah?"

"Why aren't they coming out?"

"Maybe they're full?"

"I don't think those things are ever full."

"Why don't you go down take a look?" The driver suggested as he jumped down off the back of the truck. The man who had travelled in the back of the truck jumped down as well, holding onto the top of the door as he did so that it slid down and slammed shut behind him.

"Sure they'll be out soon enough." The three of them kept their guns trained on the creek as they walked backward to the cab of the truck. They simply got back in and drove off.