Set in 2068, the series depicts a "war of nerves" between Earth and the Mysterons: a hostile race of Martians with the power to create functioning copies of destroyed people or objects and use them to carry out acts of aggression against humanity.
Earth is defended by a military organisation called Spectrum, whose top agent, Captain Scarlet, was murdered by the Mysterons and replaced by a reconstruction that later broke free of their control.
At the Supreme Headquarters Earth Forces (SHEF) building in New York, the Commander, joined by Scarlet, Blue and the reconstructed Brooks, chairs a press conference unveiling the Unitron.
Initially the demonstration proceeds according to plan, but when the Commander steps outside the blockhouse, the Unitron stops firing on its programmed targets and turns its weapons on Point 783 itself.
After requisitioning a Spectrum Pursuit Vehicle from a bazaar, Scarlet races to Point 783 and extracts the Commander and Storm while Blue remains behind with the blockhouse personnel.
Nevertheless, he expresses satisfaction with the finale, writing that the "climactic chase" between the runaway SPV and the re-programmed Unitron "just about makes the episode worth the surface-level characters and gory war politics.
Law views "Point 783" as "quite a bloodthirsty instalment" of Captain Scarlet, partly because of the violent demises of the original Storm and Brooks: while driving their car through a tunnel, they collide with a methane tanker travelling in the opposite direction.
He also states that the explosion of the reconstructed Brooks reinforces the "very alien" nature of the Mysterons, likening this self-destruct ability to the tactics used by World War II Kamikaze pilots.
Law regards the special effects as the highlight: he describes the Angels' aerial bombardment of the Unitron as "what Century 21 is, in a nutshell – fast editing, great music, big explosions and unrelenting action."
He sums up "Point 783" as "a snapshot of what Captain Scarlet is all about" as well as "visually and technically impressive, loud and exciting, yet perhaps just a tad flawed at script level".