'Girl on the Trapeze' by Dennis Spooner

A girl reportedly jumps to her death in the waters of the Thames. But when Doctor Keel pulls a different girl from the water, her dying words are “Danilov”, the name of the girl who supposedly jumped. Suspecting foul play, Keel follows the trail to a visiting circus from Radek, where he meets Vera, a trapeze girl who is looking after an injured girl whose face is heavily bandaged. Before he can question the girl, Keel and his assistant Carol are captured by Zibbo the clown, who informs them that the girl is Anna Danilov; she is to be used to blackmail her father, Professor Danilov, a scientist who has defected to the west, into returning to Radek. Keel is told that unless he informs the police that he was mistaken about the girl, Carol will be shot. But although Keel does as instructed, the police are still suspicious. Keel returns and rescues Anna, while the police arrive and close the circus down

Ian Hendry (Doctor David Keel), Delena Kidd (Vera), Nadja Regin (Anna Danilov), Ingrid Haner (Carol Wilson), Ian Gardiner (Policeman), Kenneth J. Warren (Zibbo), Howard Goorney (Supt. Lewis), Edwin Richfield (Stefan)

Directed by Don Leaver
Produced by Leonard White

TX:
UK: 11th February, 1961

Notes:
*Featuring Doctor David Keel

*This episode was suggested to the producers by Ian Hendry, who began his career in the circus (also see 'The New Avengers' - 'To Catch a Rat')

*This episode was broadcast live

*A recording of this episode was later discovered in an archive in America