The Witness

Having just played Deadline for the first time, Witness was not as good, but still very polished. As others have noted, the solution to whodunnit isn't that hard. How they did it is harder.

Again, Sergeant Duffy is here to analyze everything for you . Again, there is a death you must investigate, and a (this time smaller) cast of characters you can interrogate.

You witness the death of a man, and you must uncover the mystery behind his death (thus the name of the game).

This was Infocom's second mystery game, and (I believe) the only one by Stu Galley.