The Avengers (1961)

S06E21 Love All

Title: Love All Plot: A series of security breaches raises suspicions as high-ranking officials appear to be falling for a mysterious char lady, who is actually an undercover enemy agent. Steed takes on the challenge of uncovering the truth, but before he can delve into the investigation, he must first rescue Tara from the depths of despair caused by her unreturned affections.