Over een uiterst geheime Britse inlichtingeneenheid die bevelen ontvangt van de premier en zonder vragen de strijd aangaat met vijandige spionnen, saboteurs en andere criminelen om de veiligheid van Groot-Brittannië en de westerse Alliantie te beschermen.

The Rat Catchers is a 1960s British television series about a top secret British Intelligence Unit who receive orders from the Prime Minister and without questions battles enemy spies, saboteurs, and other criminals in order to protect the security of Great Britain and the Western Alliance. The show centred around three major characters: Peregrine Pascale Smith, the Oxford University-educated managing director with 12 years' experience under his belt, Brigadier H. St. J. Davidson, the emotionless analytical brains behind the group, and newly-recruited Richard William Hurst, formerly a superintendent at Scotland Yard who though he was said to have gone by the book in the police force, seems to have some problems with authority now. Part of the problem is that the Brigadier refuses to tell him more than the minimum that he needs to know about the organisation. Officially he works for Smith's company: Transworld Electronics and in episode 3, he is not sure whether Smith or the Brigadier is his boss.

The organisation was based at Whitehall but officially didn't exist, being denied at the highest level as they worked with the greatest secrecy. The show began with the arrival of Hurst who is out of step with the other two. Raymond Francis was originally picked for the Hurst role but changed his mind at the last minute. Many of the stories were continued, sometimes with cliff-hanger endings.