<P> Maggie Pierce (Kelly McCreary) admits to Meredith that she has a crush on Riggs, unaware of Riggs and Meredith's blossoming relationship, and asks him out, only to be rejected . Maggie is later faced with a bigger issue when she discovers that her adoptive mother has cancer and has come to Grey - Sloan for treatment; her mother eventually passes away . April Kepner (Sarah Drew) and Jackson Avery (Jesse Williams) work together to co-parent their newborn daughter, Harriet, while maintaining a platonic relationship; however, they sleep together when they travel to Montana to perform a surgery . </P> <P> As Chief of Surgery, Miranda Bailey (Chandra Wilson) appoints Meredith as Head of General Surgery and hires Eliza Minnick (Marika Domińczyk) to run the training aspect of the hospital . Though Arizona Robbins (Jessica Capshaw) goes on to date Minnick, the rest of the staff widely opposes Minnick's teaching techniques and works to get her fired, only for Meredith to get temporarily suspended in the process . Richard Webber (James Pickens Jr .) and Catherine Avery (Debbie Allen) argue over Minnick's presence as well, making their marriage more divided than ever . Owen Hunt (Kevin McKidd) and Amelia Shepherd (Caterina Scorsone) also have martial issues after Amelia reveals that she doesn't want to have kids . This causes Amelia to move out and hide out at Stephanie's apartment . </P> <P> During the season finale, a rapist is admitted to the hospital and attempts to attack Stephanie Edwards (Jerrika Hinton) and a young girl . Stephanie starts a fire to escape the attacker, resulting in the entire hospital being destroyed . Owen's missing sister, Megan, is found and transported to Seattle; Meredith reveals this to Riggs and encourages him to return to Megan, whom he was engaged to before she was abducted . </P> <Table> <Tr> <Td> <H3> Main cast (edit) </H3> <Ul> <Li> Ellen Pompeo as Dr. Meredith Grey </Li> <Li> Justin Chambers as Dr. Alex Karev </Li> <Li> Chandra Wilson as Dr. Miranda Bailey </Li> <Li> James Pickens Jr. as Dr. Richard Webber </Li> <Li> Kevin McKidd as Dr. Owen Hunt </Li> <Li> Jessica Capshaw as Dr. Arizona Robbins </Li> <Li> Sarah Drew as Dr. April Kepner </Li> <Li> Jesse Williams as Dr. Jackson Avery </Li> <Li> Caterina Scorsone as Dr. Amelia Shepherd </Li> <Li> Camilla Luddington as Dr. Jo Wilson </Li> <Li> Jerrika Hinton as Dr. Stephanie Edwards </Li> <Li> Kelly McCreary as Dr. Maggie Pierce </Li> <Li> Jason George as Dr. Ben Warren </Li> <Li> Martin Henderson as Dr. Nathan Riggs </Li> <Li> Giacomo Gianniotti as Dr. Andrew DeLuca </Li> </Ul> </Td> <Td> <H3> Recurring cast (edit) </H3> <Ul> <Li> Joe Adler as Dr. Isaac Cross </Li> <Li> Debbie Allen as Dr. Catherine Avery </Li> <Li> Tessa Ferrer as Dr. Leah Murphy </Li> <Li> LaTanya Richardson Jackson as Diane Pierce </Li> <Li> Marika Dominczyk as Dr. Eliza Minnick </Li> </Ul> </Td> <Td> <H3> Guest cast (edit) </H3> <Ul> <Li> Sumalee Montano as Lena McCallister </Li> <Li> Kimberly Quinn as Reena Thompson </Li> <Li> Rusty Schwimmer as Patricia Phillips </Li> <Li> Jen Lilley as Kara Fisher </Li> <Li> Vicki Davis as Morgan Fisher </Li> <Li> Betsy Baker as Barbara Davis </Li> <Li> Ravi Patel as Timir Dhar </Li> <Li> Bridget Regan as Dr. Megan Hunt </Li> <Li> June Squibb as Elsie Clatch </Li> <Li> Hal Holbrook as Lewis Clatch </Li> <Li> Eric Roberts as Robert Avery </Li> <Li> Matthew Morrison as Dr. Paul Stadler </Li> </Ul> </Td> </Tr> </Table>

What happens on season 13 episode 24 of grey's anatomy