When a letter bomb kills a Naval Officer whilst McGarrett is on Navy Duty, he is called upon to investigate and uncovers a plot involving an old nemesis...
| Name | Type | Role | |
|---|---|---|---|
| Orville H. Hampton | Writer | ||
| Jerome Coopersmith | Writer | ||
| David Birney | Guest Star | ||
| Wayne Ward | Guest Star | ||
| Lyle Bettger | Guest Star | ||
| Ray Reinhardt | Guest Star | ||
| Gary Kau | Guest Star | ||
| Richard Wilder | Guest Star | ||
| Lee Stetson | Guest Star | ||
| Robert Woodrum | Guest Star | ||
| Wayne Oxford | Guest Star | ||
| Sue Mullen | Guest Star | ||
| Jackie Ben | Guest Star | ||
| Morgan Shaan | Guest Star | Dr. Pendler (as Morgan Sha'an) | |
| Sally Lee | Guest Star | ||
| Harry Guardino | Guest Star | ||
| Robert Pfeiffer | Guest Star | ||
| Biff McGuire | Guest Star | Babe Mandell | |
| Robert Nelson | Guest Star | ||
| Donna Mills | Guest Star | ||
| Lloyd Bochner | Guest Star | ||
| Michael O'Herlihy | Director | ||
| Orville H. Hampton | Director |