"Manhunt" is the fourth episode of the Super-marionation television series Captain Scarlet and the Mysterons. It was first broadcast in the UK on October 20th 1967 on ATV Midlands, was written by Tony Barwick and directed by Alan Perry. In this episode, Spectrum launches a ground search for Captain Black after he becomes detectable on long-range Geiger counters.
The Culver Atomic Centre has been infiltrated by Captain Black, who is forced to quickly slip away after he is discovered by security staff. Entering a radioactive area, he is exposed to a short-life atomic isotope, which leaves him detectable on long-range Geiger counters for a period of 48 hours. Spectrum, which now has proof that Captain Black has been a Mysteron agent since being the only member of the Zero-X Mission's crew to return to Earth, begins a ground search with Detector Trucks to capture him.
In the search area around the Culver Atomic Centre, Captain Black murders a filling station mechanic to access a concealed Spectrum Pursuit Vehicle. When Captain Scarlet and Captain Blue arrive to requisition the SPV, they encounter the Mysteron likeness of the mechanic, who attempts to shoot them. But Captain Scarlet disposes of him instead. The Detector Trucks pick up Captain Black's trace as he speeds down a highway. Captain Ochre mounts a roadblock to stop him, but the Mysterons warn Captain Black of the obstruction and order him to return to the Culver Atomic Centre, where he will be undetectable to Spectrum within the surrounding radiation. The Symphony Angel, sighting Captain Black from the air, lands her interceptor nearby. She is abducted by Captain Black, who crashes the Culver gates to enter the complex.
By night, the Spectrum forces have converged on the Culver Atomic Centre. Inside, Captain Black forces the Symphony Angel into an isolation chamber and subjects her to lethal radiation, but switches off the controls before his hostage dies. Instead, he forces her to drive out of the atomic centre in the SPV. While Captain Scarlet and the others pursue the vehicle, believing that Captain Black is the driver, the entrance to the complex is left unguarded, allowing Captain Black to go through a cleansing facility to decontaminate himself of radiation before escaping. When the Symphony Angel crashes the SPV, the Spectrum ground forces realise that Captain Black has deceived them. The Symphony Angel confesses sheepishly, "It's the first time I've ever driven an SPV."
"Manhunt" introduces David Healy as a voice actor for Captain Scarlet, here providing the voices of a Spectrum Geiger counter operator and one of the Culver Atomic Centre security guards. Spectrum makes a second attempt to capture Black in "Treble Cross", which re-uses footage from "Manhunt".
The music playing on the mechanic's radio is the title music for the 1960 film Crossroads to Crime, directed by Gerry Anderson. The episode's other incidental music was recorded during a four-hour studio session held on 16 April 1967, when it was performed by an ensemble of 14 instrumentalists conducted by series composer Barry Gray. This music runs for four minutes and seven seconds. The incidental music for "Big Ben Strikes Again" was recorded during the same session.