"I've had enough time for several good looks," the Doctor shot back. He peered about the room, his head snapping left and right as if expecting River to come popping out of the cupboard with an explanation or three in her hands. "Where'd you put her? Doctor Song. Marvelous hair, doesn't seem to like you."

Obviously the Master wasn't going anywhere, otherwise he would have freed himself by now. There were a limited number of options here: either the Master kidnapped River or it was the other way around and River was doing that Thing where she thought she was protecting him by going after his best enemies. Given the fact he knew the Master much better than River, he wanted to say that this might've been his doing. Maybe. Possibly. Maybe-possibly-could be. Hard to tell! Prowling about the room, the Doctor seemed to come to the conclusion that River was in fact not hiding in the cupboard ready to brain him over the head with an explanation or three and maybe he might have better luck asking the Master.

The Doctor came up to the Master, his eyes flicking around and picking out the small telltale signs of a struggle.

"So! River and handcuffs again! I'm not surprised." He bent down to tug at the handcuffs around the Master's wrists non-too gently. "I really ought to find out where she keeps getting them."