"You will not harm these children," Rose glared piercingly into the alien's eye. "For they are my children; these are the cubs of the Bad Wolf."
"Rose," the Doctor begged her. It had taken so long for her to fully accept him to be the Doctor, he couldn't lose her now. Not to the Bad Wolf. Not again.
"The Wolf is but legend. There is no one who can hold that power, let alone a human."The alien scoffed.
"Harm them and I swear you will never do that or anything else ever again," Rose said slowly, her gaze unfaltering as she let the Wolf energy begin to flow. The alien still held the children in its long, spindly legs.
Rose's eyes began to glow as the Bad Wolf began to assert itself. "Rose, stop." The Doctor ran a hand through his wild hair, desperately trying to come up with a plan. If only human brains weren't so slow! He thought angrily, feeling helpless. He was certain that had his Time Lord self been present, the entire situation would have already been over and dealt with. But his wife and children were in danger and he was their only hope. He, who had all the memories of a Time Lord, but no way to utilize any memory to help them. He felt his pockets, hoping for an answer and found his sonic. A prototype that he had been experimenting with - it had yet to be fine-tuned (or even tested). Many of the parts had been innovated from the limited alien tech he had... borrowed from Torchwood. This Captain Jack had listened to their story and welcomed the pair like the old friends they were, albeit in another universe.
At that moment, the doors burst open, revealing Jack and a couple other Torchwood employees. Gwen and Owen, if memory served. Human brains, they took some getting used to.
"What's the situation? I'm going to assume this is a hostile." Jack's eyes hardened as he saw the captive kids. He was godfather to the both of them; Rose and the Doctor had named him and Ianto the kids' guardians should anything happen to them and he had vowed to protect them with his life if need be. Bad Wolf, however, had never been considered as an important factor in the equation (Rose had told him everything, including what had happened to his parallel self on a certain Dalek spaceship and the...surprising effects.
Owen, meanwhile, had been talking to the alien. "We can do this the easy way or we can do this the hard way. You're coming with us either way, so take your pick; I really don't care." He grunted as the alien swung a needle sharp leg towards him, grazing his ankle. Another leg was raised, about to pierce his chest when the alien was suddenly immobilized, its body covered by swirling golden energy.
"Owen, move!" Jack shouted urgently. He raced forward and pushed the other man so that Owen was safely out of harm's way. Jack, however, was now trapped with the kids. He took them into his arms, trying to reassure them that they'd be all right. Jack looked around, searching for an escape route when he glanced upward and saw the alien's fleshy underbelly. He reached up, using a pointed stick to stab the creature. "Go!" Jack told the children. The creature was writhing, presumably in pain, and flailing all its limbs. The energy of the Bad Wolf had faded; Jack hoped that Rose was okay and hadn't drained herself of her human energy. He glanced back - she was holding her kids, sheltering them from the all too threatening alien - and breathed a sigh of relief.
He had been a second too soon. A razor sharp talon pierced his chest as the alien flailed about in its own pain before collapsing, dead. He faintly heard Rose scream his name as he fell and the world seem to move in slow motion. The ex-Time Agent felt each heartbeat in his chest grow weaker and further apart and knew that the end had finally come for the man known as Captain Jack Harkness. He was faintly aware of the Doctor and Owen kneeling over him, and of the somber expressions on their faces. "Tell Ianto..." he started to say, then broke off. Ianto knew. Ianto had always known. The alien was dead and the human world was safe. He had done his job, Jack thought. This time. The last time. And darkness fell.
Rose slowly made her way to the rest of her friends, clutching the hands of her children. "Jack?" And she remembered the Battle of Canary Wharf, instantly locking with the Doctor who she knew was remembering the incident as well. Rose left their kids with Owen and walked to Jack, meeting the Doctor over his still body. "Last time Jack died... I can save him." The Wolf was fading and Rose knew that unless she unleashed it soon, Jack was as good as dead. With that realization, there was no hesitation. Rose used the Bad Wolf once more and resuscitated Jack. He woke with a start, his breathing rapid and heartbeat irregular, but alive. And, presumably, immortal.
It was only when the Doctor kneeled beside her and wrapped his arms around her that Rose realized she was shaking. She drew in Jack and the kids and held her family close.