Chief Sanders and Agent Scott investigate citizens whose loyalties are questionable, the young detectives are still curious about the coded message they found, and at the hospital, experiments reveal a patient's past.

The three sleuths argue about getting involved with the FBI investigation. Beth is concerned about Frank and the hospital experiments. Wallace is caught in the middle when Regina and Hershel argue about what's best for him.

Timmy, Arthur, and Madeline make a dangerous discovery, right under the nose of the FBI. While they investigate, Granite Flats is in an uproar - chaos breaks out at the hospital and Chief Sanders races to apprehend a suspect.

The kids' new English teacher has a way of making Hamlet applicable to life in Granite Flats. Some citizens are unsettled when a CIA agent arrives. And Arthur's detective work reaches a new level.

Ashmead stirs up confusion and danger when he meddles in the Andrews' personal and professional lives, and Chief Sanders recruits a new deputy with somewhat surprising results.

Arthur continues his investigation alone and finds a resonant soul in Whittison. Hargraves counsels Timmy on romance. And Hershel becomes the bait in a dangerous trap.

In the dramatic season finale, crisis is the watchword. Beth, Whittison, and the Andrews turn the tables on Ashmead. Timmy and Madeline find what everyone has been pursuing. And Professor Hargraves may not be what he seems.