En el metro de Londres se acumulan las desapariciones inexplicables. Algo no marcha bien, y el inspector Calhoun está decidido a descubrirlo.
 | Donald Pleasence | Inspector Calhoun |
| Norman Rossington | Detective Sergeant Rogers |
| David Ladd | Alex Campbell |
| Sharon Gurney | Patricia Wilson |
| Hugh Armstrong | The 'Man' |
| June Turner | The 'Woman' |
| Clive Swift | Inspector Richardson |
| James Cossins | James Manfred; OBE |
| Heather Stoney | W.P.C. Alice Marshall |
| Hugh Dickson | Dr. Bacon |
| Jack Woolgar | Platform Inspector |
| Ron Pember | Lift Operator |
| Colin McCormack | Police Constable 1 |
| Gary Winkler | Police Constable 2 |
| James Culliford | Publican |
