“We mustn’t change history,” Susan pouted. Ian had been so awed by her work on the portal that he’d almost forgotten she was just in her teens.

”But Susan,” said the Doctor in his softest voice, “we change history every time we step out of the doors of the ship.”

“You said that-“ began Barbara.

The Doctor whirled on her. “Do you really want to know, Miss Wright?” he said. “Do you really want to know? The TARDIS is built specifically not to change history. We can visit, we can observe, and the ship can disguise itself so no one need ever know we were there. But only so long as we never step outside. We watch it all on the scanner. My people, you see…” He paused, searching for the words.

”Doctor?” Barbara prompted.

”I couldn’t do that, could you?” he said. “It’s not travel, it wouldn’t be real. We’ve seen the most interesting things, but without stepping out of those doors, I might as well have stayed in your time, content with your television sets.”

Ian took Barbara’s hand, stopping her from responding. He knew what she wanted to say: that the Doctor had lied to them, that time in Mexico. He had lied to them about what they could do, about what their responsibilities were. He had made them feel like children, when they had been right all along. Still, recriminations could wait.