The Russian Prisoner (S05E03)

Whilst on holiday in Switzerland the Saint is approached by Irma Jorovitch who says she has come from Sweden, where she was raised by her mother, at the request of her father, a Russian professor who is in Geneva for a conference and anxious to defect to the West. However, he is being held prisoner in a lakeside chateau by Soviet officers and she begs the Saint to free him. (Prime Video)