Flashbacks show Hen and Karen meeting for the first time when Chimney sets up his neighbor, Karen, with Hen, although he doesn't tell Hen about it.

In present-day, Karen prepares to bring Denny to work with her and questions why Hen hasn't handed in her resignation papers.

Dierdra stops at home and tells Hen that Karen took them off the emergency foster list, which is news to Hen.

At the lab, Karen shows Denny around, and later, while Karen is inside the lab, there is an explosion.

In the past, Hen and Karen continue to date, and eventually, she tells Karen about her relationship with Eva.

The 118 assists at the explosion.

Hen arrives and sees that Denny is okay, but as she prepares to go in, Bobby tells her to stay outside because she is too close to the situation.

While in the lab area, the 118 puts fires out and finds Karen tending to a colleague whose arm has been blown off. After stabilizing her, the tea looks to move out while Buck escorts Karen.

Outside, Athena and Hen help one of Karen's colleagues, who writes down that there is coolant danger inside. Karen warns Bobby in time for him to save another fire captain from getting blasted by an explosive room.

Karen comes out to meet Hen but later passes out, as it's revealed that she has shrapnel lodged in her abdomen.

Flashbacks show that initially, when Hen told Karen about Eva wanting her to adopt her child, Karen said no. The two would break up until Chimney calls Karen to tell her about Hen's near-death experience. The two then reconcile.

In the present, Hen, Chimney, and Bobby work on Karen in the ambulance, and she survives.

When Karen leaves the hospital and returns home, Hen tells her that she will be going back to work at the 118.