Continuity mistake: When Harry goes to Ellie's reading carrel at Princeton Library, he leaves Sam downstairs as a watch for Professor Peabody, because he is snooping. When the Professor shows up Sam makes for the lift to go up and warn Harry. There are several cut-aways, and in the next scenes Sam is getting in the lift a second time and stands in different places. The Indian student swaps standing positions with Sam each time. (01:20:00 - 01:21:00)
Continuity mistake: In Princeton Library Harry leaves his side-kick Sam on lookout downstairs while going up to Ellie's reading carrel, to snoop on her papers. Professor Peabody arrives downstairs and Sam heads to the elevator to go up and warn Harry. There are several cut-aways showing the Professor, and Harry. Sam is entering the lift another time, also waiting in the lift just before that. (01:20:00)
