Lieutenant Colonel Victor Stans locks himself inside a rehabilitation room at an army hospital intent on committing suicide. The water temperature of a whirlpool tub is raised to the boiling point, and Stans approaches, ready to throw himself in. As a disembodied voice speaks to Stans, glass on an alarm box smashes, and the deadbolt lock to the rehab room door slides open, as if moved by an invisible force. Stans throws himself into the scalding tub, but he is quickly rescued by a nurse and firemen.

Mulder and Scully focus their attention on the case. Stans tells them a sort of phantom soldier, whom he's never seen clearly, killed his wife and child, and now wishes to see him suffer by not letting him take his own life. The agents are approached by Army Captain Janet Draper, who requests a suspension of whatever investigation the F.B.I. has begun. Protocol requires any criminal investigation of military personnel to be conducted through military channels and the superior officer.

Mulder and Scully turn to General Callahan, who accuses them of gross misconduct and labels Stans' misfortune a tragic accident. But Scully notes a similar case involving Staff Sergeant Kevin Aiklen, who also served with Callahan in the Gulf War. Aiklen claimed he, too, was prevented from killing himself by an unseen force after his family died in a tragic "accident." After the agents leave, Callahan is visited by the phantom soldier, who appears in the reflection of a window. Shortly thereafter, Draper is drowned when water from a swimming pool assumes human form and attacks her.

Mulder warns Callahan that if the pattern is at all consistent, his family may be in great danger. Callahan reluctantly admits he was visited by the phantom soldier the previous night. When Callahan returns home, his wife describes how their son Trevor saw a stranger inside the house. Scully notices someone inside the Callahan's backyard, but he escapes. A fingerprint check leads the agents to Quentin Freely, nicknamed Roach. He is charged with murder. A search of Roach's apartment turns up mail from each of the victim's homes. Shortly thereafter, as a military MP stands guard, sand from a sandbox takes human form and attacks Trevor, killing him.

During interrogation, Roach claims he is merely the "mailman" for a fellow vet named Leonard Trimble, nicknamed Rappo. The agents rush to the army hospital, where they are told Rappo is a quadruple amputee. When Mulder and Scully return to Roach's cell, they find his dead body, a bed sheet stuffed down his throat. Mulder suspects that Rappo is capable of astral projection-the ability to leave his own body and travel virtually anywhere. Before Callahan and his wife can pack up their belongings and leave, Mrs. Callahan is murdered. Despondent, Callahan seeks out Stans. He pulls out a gun and attempts to shoot himself, but the gun will not fire. Stans insists he knows the identity of the killer. Callahan enters Rappo's room at the hospital. After conversing with the amputee, Callahan decides not to kill him.

As Callahan attempts to leave the hospital, steam pipes in the sub-basement rupture. Callahan is engulfed by the hissing steam, from which emerges the phantom soldier. Mulder comes to the general's aid, but he, too, is attacked by the force. Meanwhile, Stans gains access to Rappo's room. He locks the door, and using a pillow, smothers the amputee, killing him. Back in the sub-basement, the invisible force dissipates.