Beings from the past that are like Sapphire and Steel but working for a higher power are revealed and the trap is sprung, a deception is underway but for who?

Trapped Sapphire and Steel must use their wits and the help of the tenant to escape their prison and trap the faceless man and keep him from causing more harm.

With Sapphire unconscious, Steel is unnerved by the appearance of her ghost on the railway platform with the other spirits. After 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. The soldier is not through with trying to get rid of Steel, however, and snares him in barbwire. Meanwhile, the darkness makes a deal with Tully: he can escape the station unharmed if he leaves Sapphire and Steel while they are unconscious and vulnerable.

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. The investigation becomes even more difficult and dangerous when the ghost of a fighter pilot forces Steel to experience a deadly plane crash.

The missing shop owner and missing former roommate of the tenant are found in an unexpected place. Sapphire tries to contact the missing roommate. The faceless man intervenes.

Who is the mysterious Johnny Jack from 1957 and what is his connection to the man from 1925 and the man from 1948? The woman from 1948 wants to talk to Sapphire, Steel and Silver. Silver reveals that they are trapped.

Sapphire and Steel receive a puzzling assignment at an apartment complex where time is poised to attack. However, their inspection of every room in the complex reveals nothing suspicious. Even the abandoned top floor reveals no indications of trouble. It is only after investigating the roof that Sapphire and Steel discover an invisible time-capsule from 1500 years in the future. A couple and their new baby are living inside the capsule as an experiment, but they are in grave danger because of a horrible figure hidden inside the capsule with them.

Who is the new Landlord? He confronts Sapphire and Steel but his face is not what it seems. He warns them to leave or suffer the same fate as the missing shop owner.

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 solider finally reveals what it is the darkness has promised all the ghosts but Steel gives them a better offer. 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.

Sapphire and Steel investigate strange happenings at a pawn shop. Children from the past are appearing, but how are these children connected to old photographs? What does the single tenant in the upstairs room know?

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. The kitchen is left a windblown mess and Helen and Rob help Sapphire with the clean-up effort while Lead and Steel keep watch upstairs. Everything takes a turn for the worse when two more pools of light escape from the bedroom and Rob suddenly goes missing.

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. Left alone with Helen and no neighbors nearby, Rob calls the police for help. But 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.

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. She also enlists Rob and Helen's help in removing all the objects in the house that could become hiding places for other pools of light. Sapphire and Steel welcome the arrival of fellow agent Lead, a gentle giant with a huge personality to match his huge stature.

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 Tully nearly suffocate but Steel manages to carry them to safety before the three of them meet the same fate as the young submariners. Afterward, 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.

After Sapphire disappears while trying to contact the creature inside the capsule, Steel must figure out where she has gone and how to proceed with the investigation. Luckily, technology specialist Silver arrives to lend a hand with getting inside the capsule. Rothwyn and Eldred discover their child has gone missing and are at a loss for what to do next. Meanwhile, their adult-sized infant wanders the capsule under the control of the creature hidden inside the wall.

Once Silver concocts a way inside the capsule, he transports Sapphire and Steel into the experimental pod from the future. The couple are no where to be found but Sapphire, Steel, and Silver come face-to-face with the adult-sized infant. Sapphire deciphers that the overgrown baby is a changeling controlled by time. The changeling senses that the three time agents are a threat and the force controlling the changeling commands that he destroy them.

A game of hide and seek is played before dinner but one of the guests will be murdered, there is something evil hiding in one of the guests but which one?

Two of the party guests are dead. Who will be next? This is no traditional murder mystery, and Sapphire and Steel cannot agree on who would have a motive to commit this crime.

Sapphire and Steel subdue the changeling and find where the time source is hiding in the wall. Without their technician, however, they have no way to deconstruct the wall and defeat the creature hidden inside. Steel's decision to resort to drastic measures pays off when the couple reappear in the capsule and the changeling becomes an infant again. But the creature inside the wall still thrives and presents a larger threat than anyone could have imagined.

The party guests begin to realise that they are trapped, but their memories are beginning to fail and confusion is taking over. Then there is another death. But is there really?