Mannix is poisoned, and only the poisoner knows how.
| Name | Type | Role | |
|---|---|---|---|
| Chester Krumholz | Writer | ||
| Robert Ito | Guest Star | ||
| Richard Bull | Guest Star | ||
| Grace Lenard | Guest Star | ||
| Patricia Stich | Guest Star | ||
| Sean Morgan | Guest Star | ||
| Roxanne Albee | Guest Star | ||
| Hugh Beaumont | Guest Star | ||
| Douglas Henderson | Guest Star | ||
| David Westberg | Guest Star | ||
| Bill Quinn | Guest Star | ||
| Sutton Roley | Director |