Captain Mercer looks for someone to socialize with after shift and ends up having a drink with Bortus and Clyden and playing a Moclan game that results in a knife through his hand.
Back in his room, he gets a call from Grayson and they end up having a drink together in the mess hall. Mercer admits he misses her and suggests that they try having a date and Grayson agrees. In celebration, they both have some more to drink resulting in hangovers when they're on shift on the bridge the next day as the Orville moves into uncharted space.
Bortus and Isaac detect a distortion near the star that they are about to investigate. Isaac requests the opportunity to examine the anomaly with a shuttle. Grayson offers to accompany and takes Malloy with them to pilot the shuttle.
Aboard the shuttle, Isaac detects something strange about the readings just before they are rocked by turbulence. Malloy reports that they are now surrounded by atmosphere. Aboard the Orville, the bridge crew witness an entire planet appearing out of nowhere. Getting an audio communication through from the shuttle, Grayson informs them that they have lost partial helm control and will be attempting to be set down on the planet. Mercer orders Bortus to complete multi-spectral scans to find out where the planet came from.
Malloy and Isaac set about repairing the shuttle and Grayson sets out to look around the planet. She discovers humanoid lifeforms and settlements. Despite Isaac's warning about cultural contamination, she is spotted by some children and interacts with them, using one of the Orville's medical devices to heal a head wound. When adults from the settlement approach, Grayson runs away but the child has learned her name.
In communication with the Union Admiralty, Mercer omits the fact that Grayson interacted with the locals in order to spare her the punishment for contaminating the planet's culture. Twelve hours later, they see the planet disappear again. Isaac postulates that the planet is in a multi-phasic orbit and LaMarr calculates the planet will re-emerge into their universe in eleven days. Mercer decides that they will wait and in the meantime he and Grayson have their date which is very successful.
When the planet re-emerges, Isaac detects that the planet has changed significantly in both architecture and population. Mercer orders an away team to accompany him down to the planet to investigate. They find that the planet has progressed from a Bronze Age society to something like a 14th century European one. Isaac estimates that seven hundred years have elapsed while the planet was in the other phase.
The away team attempts to steal some clothes from a farm in order to blend in but the farm woman spots them, sees Grayson, and brings out her infant son for Grayson to "bless"
Dressed in their stolen clothes, they head towards the city and discover several bodies hanging on poles. Stopping a man passing by in a wagon, they find out the dead men were "Deniers" who did not follow the local religion, The Word of Kelly.
Entering the city, they observe the name of Kelly being used to scare children and punish criminals. They find the city's central structure and discover a huge statue of Grayson in the nave.
Mercer is officially reprimanded by Admiral Ozawa for excluding the details of Grayson's contact with the planet's locals. She orders the Orville to stay in orbit until the planet achieves space travel and comes to them. They are forbidden from returning to the planet's surface. Kelly is heartbroken and retreats to her quarters to wallow.
Mercer assembles an away team and takes Grayson back to the surface with a very short time before the planet phases out. Grayson reveals herself to the head authority of the religion and tries to correct the belief system. The head priest is convinced to share the truth after the team leaves but is murdered by his subordinate.
When the planet phases back in, the Word of Kelly is still going strong. Grayson offers to stay on the planet to make another effort to correct her effect on the planet but, as she'd die well before the planet returned to this universe, Mercer refuses to allow it. Isaac offers to go in her place as he would not be affected by the passage of time.
When the planet phases back in, they have sent a ship to greet the Orville and bring Isaac back. They are a highly advanced space-traveling society now and recognize Kelly as just a part of their history now, as a mortal not a god. They now worship logic and discovery, as a perfectly rational planet.
In the mess hall, Grayson approaches Mercer and points out that their personal relationship puts both their careers in peril. Mercer understands but still acknowledges his feelings for her. She insists they put it all aside and walks away.