McCauley checks in with Spaceship M-13, which is returning from a deep-space mission. Major Summers, Johnny Ferrell, and Al Lewisham report that everything is going fine and McCauley reminds them that they have a press conference shortly after they return. Once they sign off, Lewisham detects an approaching cluster of what appear to be meteors. Summers takes evasive action but one piece strikes the ship. All systems are intact and when McCauley calls them back to tell them to wait for new reentry data because of the course change, Summers tells him what happened.
Back on Earth, McCauley and Summers meet with General Norgath, The ground crew supervisor, Major Dolan, brings in the meteor that struck the ship and explains that it's a piece of refined metal, turned on a lathe. They suspect that they may have hit a cluster of debris from an unidentified nation's spacecraft, and Norgath cancels the news conference to avoid publicity. He then orders McCauley to analyze M-13's data and plot the location of the debris cluster.
McCauley returns to his office and meets with reporter Carey Stoddart. Stoddart tries to find out what happened to M-13 but McCauley will only say that the crew is fine and the matter is under investigation. When the colonel returns that night, Mary asks about the M-13 and he repeats what he told the reporter. They're interrupted when McCauley receives a call informing him that Ferrell died in an auto accident while driving home from the base. His car went into a road excavation and the warning lights had mysteriously broken down.
Later at the base, Dolan reports to McCauley, Summers, and Captain Swanson that the metal has properties unlike any that they've ever seen, including a high resistance to heat. McCauley briefs Swanson and Summers, telling them that the three of them and Lewisham will take a spaceship to the debris cluster and gather more samples.
As they go out to conduct the postponed press conference, McCauley finds Stoddart waiting for him. The reporter informs McCauley that Lewisham drowned in a boating accident that morning. Overhearing, Summers points out that Lewisham was a competitive swimmer. Stoddart asks for a comment, pointing out that two of the three men from the M-13 expedition have now died under mysterious circumstances and Summers may be next. McCauley dismisses it as coincidence and leaves with the others, but Summers looks distinctly nervous.
Later, McCauley is at home having dinner with Summers and Swanson when he discovers that Stoddart ran a story on the "jinxed" spaceship. The colonel is eager to bring back more of the metal and prove that Stoddart is wrong. After the dinner, the McCauleys go to bed but Mary can't sleep. She finally admits that she's superstitious but her husband tells her that there's nothing to worry about.
The next day, McCauley, Dolan, and Swanson attend the final briefing. Summers hasn't arrived and McCauley gets no answer from the major's quarters. Norgath begins the briefing, explaining that the debris cluster will be in optimal position for intercept in 72 hours. As McCauley and Dolan report on the ship's modifications, they get word that Summers is dead, accidentally electrocuted in his bathroom.
Later, Stoddart visits McCauley and offers his condolences. McCauley dismisses the reporter and meets with Swanson, who mentions that he's been ordered to report to psycho-testing for recertification. When he asks if McCauley has doubts about his mental stability, McCauley says that he's concerned about both of them and goes with Summers.
Once the two officers have been certified, McCauley and Swanson meet with Major John Bowers and take the M-13 to the derelict cluster. While Dolan holds the ship steady, McCauley and Swanson go outside to gather some samples. They confirm that the debris isn't radioactive and Swanson begins taking photos. He finds one piece with a calibrated dial showing numbers in no known Earth language, and then jumps when McCauley touches him on the shoulder.
Once they secure a large piece of debris in the ship, the two men reboard and McCauley takes the ship down. The M-13 overheats and McCauley is forced to lift up out of the atmosphere and try another approach. The maneuvers stress the chain holding the debris in place, slamming it into the wall. Swanson goes back to secure it but discovers that it's jammed in place. McCauley turns the controls over to Bowers and goes back to help, but they're unable to shift it. The colonel has Bowers take the M-13 down at a steep angle to shift the debris, but the ship overheats again and he's forced to pull up before Swanson can secure the debris. McCauley has Bowers attempt reentry again and the two officers manage to secure the debris just in time before the ship's hull gives out. As they go back, Swanson wonders if the debris is cursed... and alive.
Once McCauley has secured the debris, the ship goes into re-entry and the hull reaches temperature safety levels. McCauley takes it back up but the chain holding the debris snaps. Swanson goes back to secure it before it pierces the engine room bulkhead, only to discover that it's jammed. McCauley goes back to help and orders Bowers to change the ship's altitude so they can push it back. Bowers takes it down but warns that the temperature is reaching critical. He finally has no choice but to bring it up and the debris falls over again before Swanson can clamp it in place. McCauley has Bowers repeat the maneuver and hold the altitude. Swanson finally manages to clamp the debris in place and wonders if it's alive... and cursed.
Back on earth, the McCauleys invite Swanson to dinner. When he's late, Mary worries that he's fallen victim to the curse. Swanson arrives and explains that he's late because he decided to walk, and asks if McCauley has heard from Bowers. McCauley first jokingly claims that Bowers went on a mountain-climbing trip but then assure Swanson that Bowers is in town and will be at the press conference the next day.
After the debris has been analyzed, Norgath has the reporters assemble for the conference. McCauley presents the findings, which confirm that the debris has been in earth orbit for five hundred years. They believe the debris is the result of a rocket from another world that was hit by a meteor. There's no indication of the rocket's point of origin, but a fluid low-temperature seal has traces of chlorine gas that play no part in the manufacturing. The Air Force scientists believe that the rocket's builders evolved in an atmosphere containing chlorine. McCauley ends the briefing by showing them a reconstruction of the ship based on the debris they gathered.
McCauley returns home that night and Mary keeps checking him to make sure that he's okay. Stoddart stops by with news about Swanson: he dodged one curse but suffered from another: he got married.