A.U.S.A. Robin Brooks is back in town, and her involvement in Don's case brings back memories 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 murder of a rapper puts Charlie to work analyzing the mathematics of the music business in the same week that Amita's parents come to town, and Megan has asked for a week off without discussing it with Don.
When one of Charlie's friends, a scientist at the university, is arrested for terrorist activities, it puts him at philosophical odds with Don. And as he works to prove the man's innocence, his beliefs may jeopardize his career.
The team races to find a group of kidnappers who have their victims drain their bank accounts using ATMs, and Charlie's attempt to reinstate his clearance is slowed by an agent with an agenda that may include Don.
Charlie and Don's fates hang in the balance as the team tracks a white-collar criminal through Los Angeles. Meanwhile, Alan finds out that one of his old planning projects may disappear with a new development by the city.
The death of an agent kicks everyone into high gear, but that slows down when their prime suspect turns out to have Autism Spectrum Disorder, Charlie steps on toes re-establishing himself as the resident expert, and Don looks for deeper meaning.