Saturday. The Arsenal football team and an amateur team, the Trojans, watch a newsreel previewing their imminent charity match.

Before the match, one of the Trojan's star players, John Doyce, is missing. Team-mate Raille prepares to play instead. Doyce arrives after dropping off his mistress, Gwen Lee, the fiancée of Trojan player Phil Morring. Gwen has broken off her relationship with Doyce, but he refuses to believe her.

Morring and Doyce argue in the Highbury stadium dressing room. The match begins at 3pm. At half-time, the Trojans' trainer, Francis Kindilett, attends to an injured Morring in the treatment room. A parcel is delivered to Doyce, containing a ring, which scratches him.

In the second half, Doyce collapses. The game is abandoned and a replay announced for next Wednesday. A doctor pronounces Doyce dead. Gwen, without revealing her identity, asks the Arsenal manager, George Allison, about Doyce. Allison phones Scotland Yard. Inspector Slade is rehearsing the police revue, but takes the case.

Gwen removes items from Doyce's flat. Slade, aided by his assistant, Sergeant Clinton, questions the Trojans. He learns about the parcel and the mystery girl who approached Allison. Slade discovers that a sharp object poisoned Doyce, after checking his thumb.

Slade visits Doyce's flat. The porter informs him of a mystery girl's recent visit, as well as her stay the previous night and initial departure around 2pm that day. Slade finds Doyce's diary. He learns from a neighbour that Doyce argued with a man around 1pm.

Gwen's cousin, Inga, after glimpsing a newspaper, realises that the police are looking for Gwen. Gwen refuses an explanation.

Doyce's diary details payments to an 'S'. Slade hears of an attempted break-in to the treatment room. He searches the room, discovering a sharp, pointed ring.

Slade discovers Gwen's identity after Allison and Trojan player, Setchley, recognise her picture in an advertisement. Slade questions Gwen about Doyce's quarrel on Saturday, but she is uncooperative. Morring breaks off his engagement to Gwen. Gwen accuses Inga of being in love with Morring. She threatens to tell the police about Morring and Doyce's rows.

Slade arranges for Morring to be followed. Slade and Clinton break into Setchley's home, discovering a small chemistry laboratory. Raille arrives. He admits to hating Doyce. Slade discovers that Raille, Morring and Doyce all used to play for the Saxon Rovers football team at Wyechester. Slade accuses Setchley of receiving backing from Doyce to fund his production of a new drug, Digitalin 6, the drug that killed Doyce. Setchley's sample of the drug is missing.

11.35pm. Morring arrives home to find Inga waiting. She warns him about Gwen's threat to go to the police. Slade is informed that Morring has slipped his tail. He finds Gwen poisoned with Digitalin 6. Slade discovers a cryptic message among Doyce's papers at Gwen's home.

The next day, Slade questions Morring about his movements the previous night. Later, he discovers that Kindilett founded the Saxon Rovers, and then finds a Wyechester Gazette cutting matching the message sent to Doyce. The cutting is from a report detailing Kindilett's daughter's death. Doyce had taken Mary Kindilett to a dance, but she had left early and was later found drowned. Her father found a ring by Mary's bed and believed she may have been secretly engaged. The official verdict was accidental death, but many suspected suicide.

Kindilett tells Slade about his daughter's death. Slade predicts a solution by the end of Wednesday's replay.

Wednesday. Slade and Clinton replace the ring in the re-opened treatment room. Slade adds a marking chemical around the ring's container. In the first half of the match Arsenal score. After half-time, Clinton discovers that the ring has gone. He telephones Slade, who has returned to HQ to continue rehearsals. Slade tells Clinton to arrest the player with marked hands, which turns out to be Raille. Raille, who is on the pitch, sees the police and scratches himself with the ring. He scores a goal, but is then arrested as the match ends. Slade explains that Raille killed Doyce, since Raille had been Mary's fiancée and blamed Doyce for her suicide. He killed Gwen to stop her talking.

Morring and Inga are united. Slade returns to rehearsals.