When the body of an infamous mobster who disappeared in the 1970s is found, Castle and Beckett find one remaining witness. But since he still believes it's the '70s, they must act like his delusion is real in order to find their killer.
When a Wall Street Trader is murdered the investigation is complicated when they find out the victim was a confidential informant for a US Attorney who happens to be Capt. Victoria Gates' estranged sister on Castle.
When a woman confesses to murder, she tells the detectives details only the killer would know, but when someone else confesses with the same knowledge Castle and Beckett realize this case is more mysterious than they originally thought.
As Castle Season 6 opens, Rick Castle is down on one knee proposing to Kate Beckett. But wait, she can't say yes until she tells him that she's been offered the job in Washington D.C and she really wants to take it. Thankfully, Rick is all for it. They'll make it work, together.
But being an investigator with the Attorney General's office ends up being more about politics than justice and when Kate pushes the envelope to do the right thing, she ends up without a job. It takes a little time but she ends up back with the NYPD.
Now that they're engaged, Castle worries he won't be able to shadow his partner/fiancee any longer. Not to worry. Since he isn't actually a cop, they aren't breaking any official rules as long as their personal life stays out of the precinct.
Castle season 6 is full of wedding planning with lots of obstacles. From choosing a date to finding a venue to coming up with ways for Martha to feel useful without creating giant ice sculptures of Nikki Heat.
But the biggest surprise comes when the groom gets run off the road moments before the wedding, leaving Kate Beckett to wonder what the heck happened.