The Doctor stared at Koschei, caught off-guard by that innocent conclusion, while he couldn't get the sight of Gallifrey burning out of his mind. A lie would be bad, he'd rather avoid that, so he settled on an uneasy smile instead. "Can't tell you. Spoilers."

He chose to stretch out on the bed, deciding that looking at the ceiling was without a doubt much safer right now. "So how do we build it? What do we need?" He hoped this would work. It had to, really, what other choice did they have? Koschei would want to leave this room soon, that much was certain. Maybe he ought to give Jack a warning, but how?