Checkmate is the fourteenth episode of the fourth season. It was released on 11 April 2008.
A.U.S.A. Robin Brooks is back in town, and her involvement in Don's case stirs up memories and feelings as they try to keep witnesses alive. Meanwhile, David attempts to bond with a young man who's in the chief suspect's thrall.
The chess term for the 'killing stroke', its imagery is somewhat reflected in the next episode, although logically the endgame leads to checkmate not vice versa.
Megan asks the driving instructor whether she can borrow Charlie for a minute and the instructor tells her to take the afternoon. A few minutes later, whilst Charlie and Megan are talking, the instructor tells Charlie that he's up (despite being told earlier that he was finished).
Charlie's driving instructor is trying to get him to do too many things at once. When teaching a student new skills (like pursuit driving) the instructor should only add new items after the current skill is mastered. Here he should first have Charlie master high performance driving before asking him to try to handle the radio or any other job.
The knife the assassin uses is already covered in blood before she stabs the agent watching Robin.
[This appears on the beginning of the episode] 64 squares 32 pieces 10 murders 1 dying declaration