<P> This season starts a little while after the season six finale, where the shooting in the hospital took place, and deals with the doctors trying to get their lives back to normal . Cristina seems to be the most affected by the shooting and having operated on Shepherd at gunpoint . She quits her job, feeling she no longer loves surgery, but returns . In the beginning of the season Cristina and Owen marry, while Callie and Arizona's relationship takes a turn for the worse when Arizona goes to Africa after getting the Carder Madison Grant . With Callie distraught after the breakup, she sleeps with Mark . She learns she is pregnant just before Arizona returns, confessing her love for Callie . The season also focuses on Meredith and Derek starting an Alzheimer trial, with Meredith suspecting that Adele may have Alzheimer's . Richard originally resists accepting that, but then pushes to have Adele admitted to their trial . Season Seven features the series first extended musical episode . Callie and Arizona are in a car accident that threatens the lives of Callie and her baby . The staff sing in turn as they care for and operate on Callie, heightening the emotion around the events . Mark and Arizona are forced to decide what to do if there is a choice between saving Callie or the fetus . </P> <P> Meredith learns that Adele won't get the drug in the clinical trial, but switches the papers so she can . Alex finds out and tells Hunt . At the end of the season Cristina finds out that she's pregnant, and decides against keeping the baby . Meredith kicks Alex out of her house . Derek leaves Meredith, questioning if he can have a relationship with someone who could act like that at work . </P> <P> Another central story - line in the series is Lexie and Mark . She had decided to give him another chance, but when he tells her Callie is pregnant with her baby, she has had enough . She starts seeing Jackson . </P> <Table> <Tr> <Td> <H3> Main cast (edit) </H3> <Ul> <Li> Ellen Pompeo as Meredith Grey </Li> <Li> Sandra Oh as Cristina Yang </Li> <Li> Justin Chambers as Alex Karev </Li> <Li> Chandra Wilson as Miranda Bailey </Li> <Li> James Pickens, Jr. as Richard Webber </Li> <Li> Sara Ramirez as Callie Torres </Li> <Li> Eric Dane as Mark Sloan </Li> <Li> Chyler Leigh as Lexie Grey </Li> <Li> Kevin McKidd as Owen Hunt </Li> <Li> Jessica Capshaw as Arizona Robbins </Li> <Li> Kim Raver as Teddy Altman </Li> <Li> Sarah Drew as April Kepner </Li> <Li> Jesse Williams as Jackson Avery </Li> <Li> Patrick Dempsey as Derek Shepherd </Li> </Ul> <P> </P> </Td> <Td> <H3> Recurring cast (edit) </H3> <Ul> <Li> James Tupper as Dr. Andrew Perkins </Li> <Li> Rachael Taylor as Dr. Lucy Fields </Li> <Li> Peter MacNicol as Dr. Robert Stark </Li> <Li> Scott Foley as Henry Burton </Li> <Li> Daniel Sunjata as Nurse Eli </Li> <Li> Loretta Devine as Adele Webber </Li> <Li> Jeff Perry as Thatcher Grey </Li> <Li> Nicole Cummins as Paramedic Nicole </Li> </Ul> <P> </P> </Td> <Td> <H3> Guest stars (edit) </H3> <Ul> <Li> Caterina Scorsone as Amelia Shepherd </Li> <Li> Kate Walsh as Addison Montgomery </Li> <Li> Jason George as Ben Warren </Li> <Li> Mark Saul as Steve Mastow </Li> <Li> Mandy Moore as Mary Portman </Li> <Li> Ryan Devlin as Bill Portman </Li> <Li> Frances Conroy as Eleanor </Li> <Li> Diane Farr as Laila </Li> <Li> Amanda Foreman as Nora </Li> <Li> Amber Benson as Corrine Henley </Li> <Li> Jamie Chung as Trina </Li> <Li> Adam Busch as an Fred Wilson </Li> <Li> Marina Sirtis as Sonya </Li> <Li> Nancy Travis as Allison Baker </Li> <Li> L. Scott Caldwell as Alison </Li> <Li> Amber Stevens as Laurel Pinson </Li> <Li> Laura Breckenridge as Julia </Li> <Li> Doris Roberts as Gladys </Li> </Ul> <P> </P> </Td> </Tr> </Table>

When do lexie and mark get back together season 7
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