The forerunner of all serials, What Happened to Mary was a series of twelve monthly one reel episodes, each a complete entity in itself, revolving its immediate dramatic and melodramatic problems within the framework of a single episode and designed more for story and suspense situations than action.
| Actor | Role |
|---|---|
 Mary FullerMary | Mary |
 Marc McDermottLt. Straker | Lt. Straker |
 Charles OgleRichard Craig - Mary's Uncle | Richard Craig - Mary's Uncle |
 Barry O'MooreHenry - Craig's Son | Henry - Craig's Son |
 Bliss MilfordDaisy | Daisy |
 Bigelow CooperMr. Foster - the Lawyer | Mr. Foster - the Lawyer |
 William WadsworthBilly Pearl | Billy Pearl |
 Miriam NesbittA Spy | A Spy |
| HHarold M. ShawRev. Cooper | Rev. Cooper |