A wealthy business man holds a party in a 1930s period reconstruction for his guests, but all is not what it seems. Sapphire and Steel invite themselves to investigate.

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?

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?

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 realize that things must play out exactly as before in 1930 or the human race is doomed, but something is trying to interfere with time. Dr McDee has to die.

Sapphire and Steel allow things to unfold to find the point in time when things will be changed. Only then can they ensure that time is put back on track and reset the correct future.