Sapphire and Steel

On an ordinary evening, a mother and father sing nursery rhymes to their daughter Helen before bed. Their teenage son Robert becomes alarmed when all the clocks in the house stop working. He hurries upstairs to find that his parents have vanished. A pair of strange, time-traveling agents named Sapphire and Steel arrive instead and inform Rob that they are his only hope in getting his parents back.

Sapphire and Steel determine that Helen's bedroom is the location of a time break caused by the recitation of nursery rhymes. After narrowly avoiding a disaster, Steel boards up Helen's door to prevent the creatures inside from breaking loose. Rob begins to distrust the mysterious agents and sees a chance for escape when a policeman finally arrives in the morning.

Sapphire and Steel investigate the upstairs hallway after Rob sees a pair of ghostly soldiers on the landing. Unbeknownst to them, a living pool of light has escaped from Helen's room and now lies in wait in a portrait at the top of the stairs. Sapphire walks right into the trap and disappears from the house.

Steel's drastic measures to save Sapphire and trap the pool of light prove effective, if extremely dangerous. Sapphire places the pool of light in a freezer to keep it from escaping again and tends to Steel's recovery. Sapphire and Steel welcome the arrival of fellow agent Lead, a gentle giant with a huge personality to match his huge stature.

The time break strengthens after a nursery rhyme hidden in a book becomes stuck in Helen's head. Sapphire burns the nursery rhyme book and Steel and Lead barely succeed in stopping the time break from spreading. Everything takes a turn for the worse when two more pools of light escape from the bedroom and Rob suddenly goes missing.

Lured by a vision of his father, Rob walks into a trap in the basement. A pool of light has taken him back in time to the 1700s when the house was first being built. Sapphire and Steel fear the worst when they discover that all three pools of light are there in the trap with Rob. However, Steel decides to gain the upper hand by using Helen as bait.

For their new assignment, Sapphire and Steel arrive at an abandoned railway station haunted by supernatural figures. Paranormal investigator George Tully has been observing the station because he has an interest in speaking with the ghost of a young man. They indulge Mr. Tully by allowing him to help their investigation but warn him that the apparition is something far more dangerous than a ghost.

Sapphire and Steel discover the ghost is a young World War I soldier who died in battle. They begin to suspect the railway station might be a recruitment ground for the dead. The appearance of a second ghost and the discovery of a recording with the last words of three dying submariners all but confirm their suspicions.

After Sapphire narrowly saves Steel from meeting the same fate as the doomed fighter pilot, Steel becomes determined to figure out why the ghosts are being recruited at the station. Since the ghosts have such strong emotions, Steel tries to anger the soldier into appearing by singing an old military song. His tactic works a little too well and the soldier takes out his anger on Sapphire and Tully.

Steel continues to taunt the ghost of the solider but pauses when he finds Sapphire and Tully unconscious. A hallway in the railway station has become a re-creation of a submarine where three young men died from lack of oxygen. Sapphire and Steel agree to give Tully's methods a chance by holding a séance to find more information about the solider when he was alive.

With Sapphire as a medium, Tully and Steel are able to communicate with the ghost of a woman who was once the soldier's schoolteacher. As they prod the spirit with questions, she reveals that the force helping and controlling the ghosts is a terrible, living darkness. She also gives them the name of the soldier and the details of his untimely death.

With Sapphire unconscious, Steel is unnerved by the appearance of her ghost on the railway platform. Tully agrees to watch over Sapphire's body, Steel has a chat with her ghost to determine if she is real or a trick perpetrated by the darkness. Meanwhile, the darkness makes a deal with Tully: he can escape the station if he leaves Sapphire and Steel while they are unconscious and vulnerable.

Sapphire and Steel awake to find they have been shunted forward in time twelve days. In that time, the darkness has gone and so have all the ghosts. A frightened Tully tries to convince Sapphire and Steel that he needs to leave the station for personal reasons. While Tully's bargain failed, Sapphire agrees to make contact with the darkness so that Steel can make his own deal with the enemy.

Sapphire succeeds in making contact with the darkness at a great personal risk. Steel negotiates with it by promising a powerful source of resentment in exchange for a return to present day. The darkness follows through with its part of the bargain and Sapphire and Steel must uphold their part as well, even if their actions damage time itself.