A biochemist develops a process that reverses ageing but, when he disappears, it's up to Napoleon Solo and Ilya Kuryakin to recover or destroy the process before it falls into the hands of the THRUSH.
Unfortunately the movie One of Our Spies Is Missing is not yet available on Disney Plus.
| Writing | Howard Rodman | Writer |
| Directing | E. Darrell Hallenbeck | Director |
| Writing | Henry Slesar | Story |
| Sound | Gerald Fried | Original Music Composer |
| Sound | Robert Drasnin | Original Music Composer |
| Camera | Fred J. Koenekamp | Director of Photography |
| Production | Norman Felton | Executive Producer |
| Production | Boris Ingster | Producer |
| Production | George Lehr | Associate Producer |
| Editing | Henry Berman | Editor |
| Editing | William B. Gulick | Editor |
| Art | George W. Davis | Art Direction |
| Art | James W. Sullivan | Art Direction |
| Art | Henry Grace | Set Decoration |
| Art | Jack Mills | Set Decoration |
| Art | Charles S. Thompson | Set Decoration |
| Directing | Wilbur Mosier | Assistant Director |