In 1969, US Navy SEAL Mike McCall arrives in Vietnam for his second tour. During a secret reconnaissance mission in Laos, he and his Vietnamese counterpart, Le, discover a hidden Khmer temple. When a teammate, Cook, is killed in an ambush, Mike falsifies his after-action report to protect the temple's location, an act that defines his moral trajectory. His exceptional skills bring him to the attention of Joe Kane, a former CIA officer who runs Guardian Security, a private firm in Saigon. Discharged from the Navy, Mike accepts Kane's lucrative job offer but is immediately recruited by CIA handler Dani Piedra to work as a double agent and investigate Kane's operations.
Mike quickly confirms that Guardian Security is a front for a large-scale artifact smuggling ring. His first assignment is to provide security for Jane Wade, a determined UPI journalist. Though initially wary of each other, they form an alliance as her investigation into corruption parallels his. Mike also connects with Red Thibodeaux, a jazz musician and ex-MP whose network of informants proves invaluable after his friend dies from a heroin overdose. The investigations reveal that Kane's operation is connected to a heroin trafficking pipeline run by Corsican mobster Henri Rossi, using the artifact shipments on covert Air America flights as cover.
Mike's loyalties are tested during a mission back to Laos to raid the very temple he swore to protect. Kane, suspecting a leak, forces Mike to lead the expedition. There, Mike finds Le, who has been working with local monks to move artifacts to safety secretly. Mike chooses to betray Kane, helping Le thwart the raid and escaping with him into the jungle. Kane's enforcer, Kovak, is left alive to report the betrayal.
After a grueling three-week journey, Mike and Le return to Saigon. Mike learns Kane believes he is dead and begins operating as a 'ghost' with CIA support. Meanwhile, Henri Rossi, feeling pressure from his own organization, betrays Kane by giving Jane photographic evidence of the joint heroin and artifact smuggling operation. Jane, believing Mike is dead, resolves to publish the story. However, before she can, Kane kidnaps her, intending to torture her for information and then stage her death as an overdose.
Learning of Jane's capture, Mike abandons his CIA protocols and storms Kane's villa alone. He neutralizes Kovak and Kane, rescuing Jane just as she is being forcibly overdosed. The CIA, led by Dani Piedra and Station Chief Martin, arrives to manage the aftermath. They orchestrate an official cover-up, blaming the deaths on unknown assailants and erasing all evidence of the heroin and artifact smuggling to protect their sensitive operations, particularly Air America.
In the end, Jane recovers and publishes her exposé in a local Vietnamese paper, a small victory against the official narrative. The National Police, with the information Le provides, begin the process of returning Kane's stolen artifacts to their temples. Deemed liabilities, both Mike and Jane are forced into exile by the US government. They share a final dance at Le Mistral before leaving Vietnam separately, their futures uncertain but their honor intact.
