"Where did you take him from?"

River's voice was quiet, strained. She and the Doctor stood on opposite sides of Harry's crib.

"River, it's hardly important—"

"Fine. When did you take him from, where are his parents, what were you thinking—" River's voice rose as she volleyed questions at the Doctor, to the point where Harry began to stir in his sleep.

"Shh!" the Doctor commanded suddenly, and River's mouth snapped shut at the same time Harry sighed and went still.

"They're dead," he continued, looking away from the tight expression on his wife's face. "Do you see the mark their killer left on him?"

Chastised, River bent to examine Harry more closely. She hesitated, but finally reached out and gently brushed a tuft of hair from Harry's forehead, revealing the still-dark scar. She immediately looked up at the Doctor, curiosity warring with alarm on her face. "But the only thing that could cause scarring like this is—"

"I know." The Doctor's voice was heavy. "And we'll have to deal with it. But not for a while." He finally looked at River, this time with a hopeful expression. "I thought—since we can't, I mean, you can't, and you love children, this would work. It will, won't it?"

River's eyes narrowed at that. "How did you—" her tone was sharp, but she caught herself at the last second and softened it so as not to wake the baby sleeping between them, "What makes you think I love children?"

The Doctor suddenly looked like he'd like to swallow his tongue. "Er, just a hunch—"

"And besides that, what possessed you to bring him to me in the first place? I'd make a horrible mother, I don't know what's gotten into you!"

"River," the Doctor practically cooed, reaching out to stroke her face with one hand. She lifted her chin and sniffed at him in response, but didn't pull away. He chose to take this as a good sign and carried on. "You will make a magnificent mother. And that's just what he needs, you wouldn't believe who he'd be stuck with otherwise, they're terrible. Just terrible."

The Doctor might have carried on with his coaxing, but River's eyes widened almost comically as his words sunk in properly. She took his hand in both of hers and pulled it away from her face so she could concentrate, closing her eyes as she focused on Harry…

A half-second later her grip tightened painfully on his hand as her eyes snapped open.

"You've changed his timeline!" She carried on quickly before the Doctor could protest, not remembering to mind her volume in her shock. "Not just his, either, you've diverted an entire time track—"

The Doctor's face fell and Harry began to stir again, but this time the two adults in the room were paying him no attention.

"Sweetie," she said, this time sympathy softening her tone, "surely you realized this wouldn't work. There are too many timelines intertwined with his. His fate—"

"Fate," the Doctor echoed her, something like spite in his tone, but River soldiered on unphased.

"—must stay on course, and you know it."

Their conversation might have continued indefinitely, but as fate would have it, at that moment Harry finally woke up properly and, finding himself in an unfamiliar place surrounded by unfamiliar people, began to cry.

The Doctor and River looked down at him, startled, then at each other, communicating silently; the Doctor with a pleading expression, River with a faintly stricken one. After a tense few seconds, River was the one to give in. She released the Doctor's hand and gently scooped Harry out of the crib, hesitating for only a second before properly cradling him in her arms.

Unlike the Doctor, her movements were hesitant and stilted; she had little experience with small children. But some things come naturally, and a small smile crept across the Doctor's face as he watched them.

"We can do this," he said quietly as River rocked Harry back to sleep. "Time will bend for us."

In River's arms, Harry's crying tapered off into whimpering and he curled against her, gripping her shirt with one tiny hand. River seemed to be entranced by him.

"Trust me," added the Doctor, and when River finally deigned to look up at him the expression on her face told him he'd won.

In the greater scheme of things, outside the TARDIS where River Song was slowly adjusting to the idea of motherhood and the Doctor was occupying himself by rearranging his ship, creating new rooms and generally rushing about with all the aplomb of an overexcited toddler, a time track that had once been relatively set in stone adjusted itself to a new, winding course. In 1981, Sirius Black howled in grief and reacted too quickly, and his poor impulse control sent him to the wizarding world's worst prison. Ministry workers searched the Potter residence and found no sign of the Dark Lord or his youngest victim. Minerva McGonagall's evening was interrupted only by celebration (and mourning), with no late-night trips across the country, and the following morning when Petunia Dursley stepped outside to get the milk there were no unpleasant surprises waiting for her.

As for the more severe consequences of the Doctor's choice…only time would show them.