Fish on the hook is one of my favorite episodes from either the 1/2 hour or 1 hour Danger Man series. There is something happening every moment, and mostly it's things going wrong for John Drake. An extremely well placed source in a foreign nation feeding information to the British government is suddenly compromised and must be extracted within 24 hours.
The things is, the leaker has buffered themselves with four layers of contacts, each of whom Drake must discover and interrogate in order to iterate to the source. Pay close attention in the first few minutes as these contacts are revealed, else you may get lost.
There is a wonderful moment about 2/3 way through the episode where Drake has both a male and female antagonist to deal with at once in the corridor of an office. Watch how Drake subdues each if them nearly simultaneously. It's rather hilarious.
Guest Star Alumni! There are several guest stars from other Danger Man's appearing in this story. Drake's primary contact, Gerdi, is played by Dawn Addams, who also appeared in 'The Battle of the Cameras', the most Bond like Danger Man ever made (Drake in a tuxedo in a casino). Great episode!
Actress Zena Marshall, who plays the wife of the prime minister, appears in two of the earlier 1/2 hour series; 'The Leak' and 'Find and Return', playing a doctor and a jilted wife respectively. Both shows are well worth viewing.
Then you have exquisite character actor Martin Miller who plays a doctor in this episode. He plays an eccentric bomb maker in an earlier 1/2 episode called 'The Lovers'. Another good episode.
At least three other cast members also appeared in other Danger Man episodes. I'll let you look those up on you own. ;>