Luther Gage, an egomaniacal, methodical killer whom Dr. Hyatt helped send to prison, vows revenge and conducts a plot planned to the last detail to carry it out. Checkmate employs the services of Chris Devlin, seen here for the first time, to enter the prison posing as a new inmate to figure out and thwart Gage's plan.
| Name | Type | Role | |
|---|---|---|---|
| Lewis Reed | Writer | ||
| William Shatner | Writer | ||
| Jack Betts | Guest Star | ||
| Jack Mann | Guest Star | ||
| William Bramley | Guest Star | ||
| Ina Victor | Guest Star | ||
| John Zaremba | Guest Star | ||
| Robert Williams | Guest Star | ||
| Olan Soule | Guest Star | ||
| Ken Lynch | Guest Star | ||
| Tony Randall | Guest Star | ||
| Leo Penn | Guest Star | ||
| Paul Stewart | Director |