Luke's alibi seems very legit; he told me a few days ago that he had a dentist appointment (11 I think?) and therefore would take some train home which would be at earliest the 12:05 one arriving at Yawkey at 13:26 (
http://www.mbta.com/schedules_and_maps/ ... e=WORCSTER), the time he said, and he remembers being impressed by how exactly timely it was; MIT is a further 7-10 minute uber ride. He also has compelling evidence for having not just made the whole thing up (showing me new toothbrush etc. from the dentist, and unrelatedly telling me stories about things his family said). That said, I suppose he could've gotten his family to drive him back so as to have an alibi... I am marking this gray.
I had previously thought Lucy couldn't have gotten to campus that quickly, but I think the timing actually checks out if she had hurried and had reasonably lucky traffic, based on google maps.