While holidaying in Paris, the Doctor and Romana experience cracks in the fabric of time.
Templar receives a request for protection from a beautiful girl (June Ritchie) claiming to be Hitler's daughter; guest Noel Purcell.
The Doctor discovers that Professor Kerensky is conducting experiments in time for the mysterious Count Scarlioni.
The Doctor learns the truth about the Count and Scaroth. Can he get back to Paris in time to save Romana and Duggan?
The Count threatens to destroy all of Paris to make Romana help him complete his machine. Can the Doctor prevent him using it to wipe out the human race?