In an old house filled with old antiques, a nursery rhyme ("Ring a Ring o' Roses") read aloud causes a time fracture that takes away the parents of youngsters Rob and Helen. As Rob (Steven O'Shea), Helen's older brother, tries to call the police, two mysterious strangers calling themselves Sapphire and Steel arrive to fix the problem. Lead also arrives to provide assistance to Steel when the ghosts of the time corridor incapacitate him.

In an abandoned railway station, parapsychologist George Tully conducts an investigation, as two operators, Sapphire and Steel arrive for an investigation of their own. A malevolent, growing force identifying itself as the Darkness is feeding on the resentment of the dead, using as a focus Private Sam Pearce, the apparition of a World War I soldier shot and killed eleven minutes after the armistice had been signed at the eleventh hour of the eleventh day of the eleventh month in 1918. The Darkness 'recruits' other resentful shades from the past who also died unfairly as a result of coming or completed wars. Sapphire and Steel must decide if the life of one living human is worth the price of the danger presented by the growing Darkness.

Rothwyn and Eldred, a couple living in a modern apartment with a baby, are from the 35th Century, the apartment is their time capsule, which is situated and cloaked on the roof of a present-day tower block; in a test to live as 20th century humans. But trouble starts when the couple discover that they can neither contact their controllers in the future nor two other similar time capsules in the present day. The biomechanical system that runs the capsule has an agenda of its own, one of vengeance. This time, Sapphire and Steel have help in the form of Silver, an inter-dimensional operator.

Phantom children with sepia-toned skin play in the back yard of an aging apartment building and its adjoining antiques shop which is currently closed. Both the landlord Mr Williamson and a tenant named Ruth have mysteriously disappeared. A man without a face in cahoots with the children, appears on the stairs. An evil presence has emerged from a photograph; something which has appeared in every photograph ever taken anywhere in the world, and is powerful enough to turn Sapphire and Steel into literal two-dimensional photographs of themselves.

Wealthy industrialist Lord Mullrine hosts a party at his mansion where he and the guests reenact the 1930s. The occasion is to celebrate fifty years since his company was founded with the late virologist Dr George McDee. Mullrine has even gone so far as to have every room in the house, with the exception of his private office, put back to its original style. Sapphire and Steel arrive under an alias, then, time itself starts to interfere. McDee turns up, alongsidr other anachronisms, and then, one by one, guests begin to be murdered — their bodies vanishing. Secrets and lies involving McDee and a marital affair from fifty years before are resurfacing, Time is playing a deadly game, and only Sapphire and Steel can end it.

At an abandoned service station and its adjoining café, time has stopped. Operator Silver has arrived first assessing the situation. Sapphire and Steel remain uncertain as to exactly what they are supposed to be investigating. The key may lie in two humans in the café who claim to be from 1948, a service station worker, and a travelling performer, but something envious and sinister gets closer before a trap is sprung.