"Dangerous Rendezvous" is the twentieth instalment of Captain Scarlet and the Mysterons. Written by Tony Barwick and directed by Brian Burgess, it was first broadcast on 9 February 1968 on ATV Midlands.
In this sequel to "Crater One Hundred And One" and "third part" of the "Lunarville Trilogy," Spectrum uses the crystal taken from the Mysteron outpost on the Moon to contact the enemy and propose a truce between Earth and Mars.
Following the destruction of the Mysteron outpost on the Moon, Dr Kurnitz of the Nash Institute of Technology has discovered that the crystal removed by Spectrum can be used to communicate with the Mysterons on Mars. Captain Scarlet escorts Kurnitz to Cloudbase, where an interplanetary transmitter has been constructed. Meanwhile, the Mysterons threaten to destroy Cloudbase at midnight.
Kurnitz activates the transmitter and Colonel White addresses the Mysterons. Recalling the Zero-X mission to Mars, White insists that the attack on the Mysteron city was motivated by fear, not hostility, and ends his broadcast with an offer of peace. Two hours later, the Mysterons respond: they agree to negotiate on the condition that a lone Spectrum officer, unarmed and without communications equipment, depart Cloudbase on a bearing that will take him over Greenland. Scarlet volunteers for the mission and leaves in a Spectrum Passenger Jet.
After crossing the Greenland coast, Scarlet ejects on the orders of the disembodied Mysteron voice. He is picked up by a car under Mysteron control and driven to a shack containing a pulsating glass screen, behind which Captain Black is sitting. Instructing Scarlet to relay a "message" to humanity, Black starts a tape recording – in which the Mysterons re-affirm their intention to destroy all life on Earth – and departs. Scarlet smashes the screen to find a second Mysteron crystal, which begins to pulsate violently. He escapes the shack just before it is destroyed in an explosion.
Realising that the first crystal is also a bomb, Scarlet takes the car and speeds to an unmanned radar station, where he transmits a warning to Cloudbase in Morse code. Seconds before midnight, White decodes Scarlet's message and orders Captain Ochre to shoot out one of the base's observation windows and jettison the crystal, which explodes harmlessly in the atmosphere. Later, White says that Spectrum remains committed to finding a peaceful solution to its war with the Mysterons.
The conclusion of a three-episode story arc that began with "Lunarville 7", "Dangerous Rendezvous" was actually filmed before the previous instalment, "Crater 101". It was shot back-to-back with "Traitor" on Century 21's Stage 3.
When Tony Barwick wrote "Dangerous Rendezvous" and "Traitor", filming on Captain Scarlet was several weeks behind schedule. To remedy this, Barwick included a flashback to the first episode, "The Mysterons", in each script to reduce the amount of new footage that would need to be filmed, enabling both episodes to be shot in 15 days instead of 20. Although the script for "Dangerous Rendezvous" allowed for approximately four minutes of recycled footage, the flashback in the finished episode – in which Colonel White recalls humanity's disastrous first contact with the Mysterons – runs for approximately two minutes.
Besides recounting the event that triggered Earth's war with the Mysterons, "Dangerous Rendezvous" was also written to explain a number of Spectrum protocols: the wait for the Mysteron reply is extended by scenes in which White, Captain Scarlet and Captain Blue, at Dr Kurnitz's request, give an overview of the organisation's communications (specifically its cap radio technology and call signs) and put on a demonstration Angel launch.
"Dangerous Rendezvous" marks the return of Spectrum's security tanker "Yellow Fox", slightly modified from its first appearance in "Winged Assassin". Cloudbase is threatened with destruction for a second time in the series' penultimate episode, "Attack on Cloudbase".
Footage from "Dangerous Rendezvous" was incorporated into the 1981 Captain Scarlet compilation film Revenge of the Mysterons from Mars.
"Dangerous Rendezvous" is named the worst episode of Captain Scarlet by TV Zone magazine, which describes it as an anti-climactic "low-key effort" that "ends a trilogy of otherwise superb episodes on a let-down ... wasting two episodes' worth of superb build-up". Anthony Clark of sci-fi-online.com comments that while the pace of the episode "could hardly be described as breakneck", along with "Crater 101" and "Shadow of Fear" it helps to "progress Spectrum's fight back against the Mysterons".
Chris Drake and Graeme Bassett suggest that the scenes of White, Scarlet and Blue explaining Spectrum's communications add interest to the episode. Chris Bentley argues that they are simply padding, comparing them to the expository Stingray and Thunderbirds mini-albums A Trip to Marineville and Introducing Thunderbirds. Drake and Bassett question White's logic in ordering a demonstration Angel launch while Cloudbase is under threat.
Media historian Nicholas J. Cull suggests that the premise of "Dangerous Rendezvous" was inspired by contemporary events, arguing that the possibility of a truce between Earth and Mars echoes "shifting attitudes within the Cold War" during the 1960s. Comparing "Dangerous Rendezvous" to other episodes written by Tony Barwick, Cull observes that Barwick's scripts often "reflected a yearning for détente and an alternative to the divided world."
The British Board of Film Classification certifies the episode U, noting that it contains one "very mild" instance of violence.