The sixth season of this crime drama opens with Beckett (Stana Katic) accepting a marriage proposal from Castle (Nathan Fillion). However, their road to the altar gets a little bumpy when Beckett also accepts a new high-profile job in Washington, D.C. Meanwhile, things don't go smoothly for Castle and Alexis (Molly Quinn) when he doesn't approve of the new boyfriend she's brought home from Costa Rica. Castle gets a glimpse at what parenthood would be like a second time when he and Beckett temporarily care for a baby who was carried into a church by a man dying from gunshot wounds. And Ryan (Seamus Dever) and his wife excitedly prepare for their first child, but she goes into labor while Ryan is investigating a dangerous arson case.

Ever since their daughter was born, it was only a matter of time before Brennan (Emily Deschanel) and Booth (David Boreanaz) finally tied the knot. And while they do say "I do" in Season 9 in a TV wedding for the ages, it's not before an unforgettable proposal that involves the diabolical Christopher Pelant (Andrew Leeds), whose obsession with Brennan brings them closer than they've ever been. Of course, the couple's honeymoon in Buenos Aires turns into a busman's holiday when they help a detective investigate the murder of a Nazi war criminal. Back at the Jeffersonian, Angela (Michaela Conlin) and Hodgins (T.J. Thyne) discuss having another child; Sweets (John Francis Daley) takes a leave of absence; Cam (Tamara Taylor) is the victim of identity theft; Clark (Eugene Byrd) writes a novel; and Wendell (Michael Grant Terry) is jolted by news that could affect his future at the lab.