Shamus

Victor Papas is attacked at his home and burned to death with a flamethrower, killing him and his girlfriend. Private detective Shamus McCoy, based in Brooklyn, is hired by E.J. Hume to recover the stolen diamonds and identify the killers. Hume claims Papas stole diamonds from him, and McCoy wonders why he was chosen for this dangerous assignment.

McCoy accepts the case after weighing the high fee and the promise of a substantial payout. He starts assembling his network of contacts to dig into Papas' background. The assignment is framed as a diamond recovery and murder investigation.

Using his informant Springy and a drug dealer, McCoy uncovers that Papas and his girlfriend worked for River Edge Export. The revelation hints at a larger criminal operation behind Papas' murder. McCoy realizes the case may involve powerful corporate players.

Springy explains that Felix Montaigne, a famous former football player, is the president of River Edge Export. Montaigne rose to power after acquiring the company and amassing a secret fortune. This links Papas to the company's criminal activities.

Shamus tracks down Bolton, the bar bouncer linked to Papas. After a confrontation at closing time, Bolton reveals that Felix Montaigne killed Papas. The information confirms Felix as the killer, and McCoy records the lead.

The next morning, McCoy visits Felix Montaigne's luxurious apartment. Alexis, Felix's elder sister, appears and hints at secrets surrounding his business. Felix admits Papas and his girlfriend worked for River Edge Export but refuses to name any partner.

A few days later, Shamus is attacked by three thugs warning him to drop the case. Alexis visits McCoy and asks him to investigate Felix, leveraging McCoy's attraction to her. McCoy agrees to continue the investigation.

McCoy sneaks into River Edge Export's warehouse and discovers a cache of weapons and a dead body. He is discovered by a trio of assassins but manages to escape. He learns that E.J. Hume is a major shareholder and realizes the case implicates national-level smuggling, prompting him to withdraw.

To verify the arms connection, McCoy disguises himself as a weapons dealer and visits Colonel Hardcore at the Army Weapons Depot. The colonel admits that River Edge Export is buying illegal weapons, then is killed by two men in a car as McCoy barely escapes.

The investigation reveals that Felix murdered Papas and stole the diamonds. Hume, unaware of the full extent of Felix's crimes, orders McCoy off the case while fearing exposure of his own arms-smuggling operation. Springy is killed by an unknown assailant.

McCoy breaks into Hume's mansion to confront him and is bitten by Hume's ferocious dog, making capture easy for Hume's minions. Inside, he finds Felix beaten and near death, a clue to the hits that felled Papas.

Outside, McCoy fights his way free, and Felix is shot to death during the ensuing struggle. McCoy subdues Hume's minions and stops Hume from escaping in a car.

The police arrive and arrest Hume, ending the conspiracy McCoy uncovered. The diamonds and murders are tied to the chain of events McCoy exposed, bringing the case to a close.