Series 4, Episode 2: 'Catherine the Great'', tx. 21/2/1974

Commander Fletcher and DI Craven are attempting to intercept a contract killer called Helmut Rehfuss. They inspect a passenger ship, but Rehfuss, who uses a drag act as a cover, escapes the ship dressed as a woman, with his companion Helga following at a safe distance.

Rehfuss performs his act 'Catherine the Great' in a lively drag club. Adrian Penfold, an old acquaintance, meets him backstage. Rehfuss asks Penfold to get him a gun, and uses blackmail when he seems reluctant. Meanwhile, Fletcher and Craven learn from the German police that Rehfuss normally carries out political assassinations. CID come up with a lead on a gun supplier, and the investigating officer is Bill North, a former Special Branch officer who Craven had transferred to CID because he refused to shoot a man in cold blood.

Craven meets North and they bury their differences. North explains that they are keeping tabs on Penfold. Later, Rehfuss collects his gun, and then murders Penfold. Craven and North are baffled as to how Penfold's killer could have evaded the surveillance team, but North mentions that he saw a red-headed woman enter Penfold's shop. Rehfuss returns to Helga, and she is shocked that he has murdered Penfold.

Craven realises that they are dealing with someone disguised as a woman, and works out that Helga must be accompanying Rehfuss. Strand, the MI5 operative, tells Craven that Rehfuss's target is likely to be Yqueras, the leader of Domago, who is under threat from the Domago Liberation Party. Craven and North visit the drag club where Rehfuss performs, and decide to put him under surveillance. DI Ross talks to Yqueras's son about possible threats to his father's security, and he seems troubled. Strand arranges to hide Yqueras on a houseboat for a few days, but Craven doesn't know that Rehfuss has already been told of this change of plan, and is waiting by the river.

Yqueras is persuaded to hide on the boat. Rehfuss and Helga argue, and he kills her in cold blood before escaping surveillance. North arrives at the boat to help Craven. Rehfuss is about to shoot Yqueras but North wounds him, and gives chase. Meanwhile, Yqueras's son is revealed as a traitor and makes a run for it, but is caught by a bodyguard. Rehfuss is surrounded, and while attempting to shoot his way out is killed by North.