While traveling in a Runabout, Kira and Odo learn that a Maquis ship has ambushed a Lissepian vessel. They pursue the attacking ship to a deserted moon, where it crashes. Kira and Odo land on the moon, which is virtually uninhabitable and rocked by seismic activity. They split up within a group of caverns where the fugitive may be hiding, but Kira soon summons Odo with a distress call. He hurries to her side to find a crystal formation growing around Kira's foot, trapping her.
The crystal, which Odo cannot break, rapidly grows to just above Kira's knee. Atmospheric interference makes it impossible for him to either free her with the Runabout's transporter or send a distress signal back to the station. Odo then returns to the caverns to hear the sound of phaser blasts. Kira says that she just exchanged shots with the Maquis fugitive, but both missed. This, however, is the least of her problems — both her legs are now entirely covered in crystal.
Tremors shake the cavern while the crystal continues to grow around Kira. Odo brings in equipment to build a makeshift ultrasonic generator in an attempt to shatter the crystal. It has now grown to cover Kira's rib cage, making it difficult for her to breathe. Odo realizes that finding the right frequency might take longer than the few hours left before Kira is covered completely, but he is determined not to leave her stranded, and they betray just a bit of emotion toward each other. Then, suddenly, the cavern is shaken by a powerful tremor.
Odo morphs into a dome to shield Kira and the generator from the falling debris. But after trying every possible frequency, the crystal remains intact and grows to reach the middle of Kira's chest. Realizing there is nothing more Odo can do, Kira orders him to leave and save himself.
Odo refuses to go, despite Kira's reminder that if he stays, he will die along with her. But Odo says he cannot leave — because he is in love with Kira. After a moment, Kira shocks Odo by replying that she is in love with him, too. The increasingly suspicious Odo remains virtually silent for an hour, while the crystal grows up to Kira's neck. But when Kira then admits she isn't really in love with him, Odo realizes that she would never risk their friendship by lying. He points a phaser at her and demands to know what happened to the real Kira. The woman and crystal then morphs into the female shapeshifter Odo met when he discovered his homeworld. Knowing Odo's feelings for Kira, she planned the entire scenario to trick Odo into believing Kira died, hoping this would prompt him to return home. Angry, Odo makes her reveal Kira's location, and he then rescues his friend. They then return to the station, with Odo's deepest feelings still a secret from Kira.