The Orville bridge crew are watching an episode of Seinfeld and most are enjoying it. Isaac does not understand the humor and Malloy offers to teach him the art of the practical joke. Kitan receives a distress call from a nearby star and they discover a mining ship crashed on a comet approaching the star.
The captain of the mining ship, Pria Levesque, requests help and Mercer, Kitan, and Malloy have to take a shuttle down to rescue her. They manage to get her but then the shuttle is nearly sucked into the star by its gravity. The Orville locks on with a tractor beam and brings them in.
Malloy plays a practical joke on Isaac by dressing him up with Mr. Potato Head pieces.
Levesque turns out to be from a town near where Mercer grew up. After a social gettogether, Levesque returns to Mercer's quarters and thanks him personally, kissing him on the cheek.
Grayson checks into Levesque's story and she does not appear in the employee database of the mining company she claims to work for. Mercer gives Levesque a tour of the ship, specifically the engineering department and the engine core.
Grayson informs Mercer of Levesque's non-existence in the mining company's records but he refuses to investigate his guest. Grayson then seeks out Kitan and convinces her to search Levesque's quarters. They find an unscannable rectangular object under her mattress but are interrupted by Levesque's return to her quarters.
Mercer reprimands both Kitan and Grayson for the search of Levesque's quarters. Grayson accuses him of not being objective and he accuses her of being jealous. Suddenly the ship lurches and Bortus asks the captain to report to the bridge. The ship is being pummeled by invisible forces. Isaac figures they are in a concentrated dark matter storm. Levesque rushes to the bridge and gives them advice on how to make the dark matter visible. They are seemingly surrounded. The Orville is taking massive damage and Levesque asks to take the helm in order to get them out of the storm.
Mercer gives her helm control despite Grayson's misgivings and Levesque manages to safely maneuver out. The communications array is destroyed and the nearest Union base is five days off course. Levesque offers to guide them to a nearby mining outpost for repairs and where she can be dropped off.
Mercer takes Levesque to the environmental simulation deck to share a favorite program. They kiss and Mercer suggests they take it slow due to his recent divorce. They have sex.
Malloy is woken up by an alarm but falls over when he gets out of bed because one of his legs has been amputated from the knee down. Isaac's practical joke has struck.
Newton asks Mercer and Grayson to come see him in Engineering. Yaphit found an object in one of the ship's relays and Grayson identifies it as the object she and Kitan found in Levesque's quarters earlier. It cannot be removed without possible damage to the relays.
Mercer, Grayson, and Kitan confront Levesque in her quarters and demand she explain herself. She claims to be a time traveler from the future and tells them that they were meant to die in the dark matter storm. When Mercer expresses disbelief, she takes over the helm through a control embedded in her forearm. When Grayson asks why she'd travel back to save their lives, she tells them it's the ship she wants. Mercer doesn't get why the Orville would be worth anything to someone from the 29th Century. Levesque explains that she's a dealer in old artifacts, mint condition. She plans on taking the crew with her to the 29th Century.
While they're discussing the situation, Malloy's leg falls out of the ceiling.
After a high-beam weapon fails to dislodge the controlling device, Newton uses an old-school drill on it. Issac accesses the internal circuitry through the hole and then is blasted across the room. Newton scans him and pronounces him "dead".
In sick bay, Malloy is having his leg regenerated but forgives Isaac for the leg thing, admitting it was the best practical joke ever. Mercer orders Malloy to the bridge. As they approach the wormhole, Levesque teleports to the bridge to guide them to the rendezvous point. Mercer begs her to give him back his ship.
The Orville travels through the wormhole and Levesque starts haggling with her clients. While she's distracted, Mercer notices a message at his com and realizes that Isaac is in the ship's computer and has control. Springing into action, Mercer orders the ship to go back through the time line. Grayson takes the opportunity to put the beat down on Levesque. Once back in their time, Levesque is thrown in the brig.
To solve the potential time-line issues, the Orville destroys the wormhole Levesque has been using to travel back and forth, causing her to fade out of their existence.