Mercer informs his senior crew that they will be picking up Admiral Christie and taking him to the Krill to begin negotiations for access to the N'klav sector on the other side of Krill space.

Dr. Finn is not enthusiastic about the news. When Talla comments on her reaction, she covers by saying she didn't sleep well.

Christie visits Dr. Finn in sickbay as soon as he arrives. He was one of her professors.

He tries to make dinner plans for them and is surprised to hear she has kids. Before he leaves, he apologizes for something that happened twenty-five years ago.

A diplomatic reception is held when the Orville rendezvous with the Krill. One Krill negotiator is clear that the alliance is only because the Kaylon are still a threat.

Christie makes a rousing toast to a better future. Dr. Finn leaves the room quickly with a bottle of alcohol and invites Grayson to join her.

As they drink, Dr. Finn discloses that she was once married to Christie.

As negotiations get underway, the Krill are willing to grant passage in exchange for mineral extraction rights on an uninhabited planet in Union space.

Christie asks for cartographer information on the K'Lar Expanse. The Krill warn them off exploring the Expanse, describing it as a domain of evil. Christie states their intention to explore it.

They part after an agreement is reached. Christie offers thanks. The Krill offer a prayer for those about to die.

Christie, Mercer, and Grayson discuss the Krill warning with Admiral Halsey over a video link. Mercer is willing to take the risk and Halsey gives his blessing.

Christie finds Dr. Finn having dinner at Mooska's. He informs her he'll be coming with them to the N'Klav sector. He shows her that he's brought his wedding band with him as he always does whenever he travels. She is clear with him that she no longer harbors romantic feelings for him.

Mercer gives a ship-wide address as they prepare to begin their mission.

Christie visits Isaac in his lab and asks his advice about Claire as they've both had relationships with her.

The ship arrives at the N'Klav Sector. Talla reports a distress signal coming from the K'Lar Expanse. They enter the Expanse, noting there are no stars.

Once in the Expanse, they discover a space station structure shaped like a spider.

Mercer leads an exploratory team to the station which opens a portal to admit the shuttle.

The walls of the station's corridors are covered in an unknown organic alloy. The team splits up to investigate.

LaMarr and Talla find an automated beacon which is the source of the distress signal.

As Christie examines a glowing structure on the wall's surface, it suddenly blossoms and then contracts closed again.

As the team debriefs back on The Orville, Christie suddenly collapses, making sounds of pain. His face is disfigured and he continues to spasm.

In sickbay, Dr. Finn discovers that something is rewriting Christie's DNA at an alarming rate.

Another team is sent over to gather more information, this time in EV suits. Mercer and Talla collect a sample of the microparticulate that Christie was hit with. Meanwhile, LaMarr discovers the beacon has changed its message from a distress signal to the coordinates of the outpost.

Christie wakes up in sickbay and he and Dr. Finn talk. He asks that she put his ring back on his finger in case he dies.

While Mercer and the team inform Dr. Finn of their discovery, Christie disappears from sickbay.

When the bridge is notified, Bortus tries to alert security but the ship's power controls are highjacked by someone using Level 9 command codes.

Grayson sends Bortus and Isaac to Engineering to access auxiliary power.

Dr. Finn leaves sickbay to check on her kids. Nurse Park is left alone. When he goes to investigate a noise, he finds a pile of stained clothes and turns to be confronted by a fully transformed alien monster.

Mercer, LaMarr, and Talla dock their shuttle manually. The ship-wide dampening field renders their weapons and coms useless.

As Dr. Finn searches her quarters for her sons, Marcus and Ty have made their way to sickbay to look for her.

Mercer and Talla find Grayson, Malloy, and Burke.

LaMarr goes to Engineering and decides to look for the source of the dampening field.

Ty and Marcus spot the spider-alien in the mess hall. They hide from it. Lt. Woodson finds them but before they can go far, the spider-alien jumps on Woodson and spits in his face. He immediately transforms into another spider-alien.

The Finn boys run away and run right into Dr. Finn. They tell her what they saw and she decides to head to the bridge.

Talla goes to look for LaMarr after Mercer's senior crew figures out what's happening and how the Krill might've interpreted it as demonic possession.

Dr. Finn and Bortus head back to sickbay to research a counteragent.

A spider-alien finds LaMarr and chases him out of the conduits. He escapes only to be chased by two others. He escapes them by sealing himself into a brig cell.

Talla hears them, comes to the brig, and lures them away. She fights them off in the cargo bay.

Isaac is confronted by an alien in the corridor. It examines him closely and then leaves. Isaac hears LaMarr calling for help and lets him out of the brig.

LaMarr gets communications back up and Mercer contacts Finn. She needs to examine one of the aliens. Just then, Talla brings in an unconscious alien.

Malloy alerts them that a vessel is approaching. It appears to be responding to the homing beacon from the outpost.

Dr. Finn examines the alien and realizes it was a human crew member. The white blood cell count is extremely low and she hypothesizes that the transformation reduces the victim's immunity to nothing. A synthetic virus could wipe out the aliens onboard.

Mercer wants to give the aliens who were once crewmates a chance to leave peacefully. Dr. Finn asks Talla to find Christie by searching for the rare mineral his wedding ring is made of. She offers to try to communicate with him.

They find the Christie-alien in Engineering. She tells him about the toxin. He threatens to change all of them. She orders the toxin to be released. He contacts the other aliens and says that they'll go but not forever.

Isaac finds Dr. Finn in Mooska's to check in on her. He offers her condolences on the loss of Christie and shares the fact they spoke together about her. She tells him she's missed him and asks him to join her.