BANG! BANG! BANG! BANG! Castle is baffled to see Henri and the masked gunman dead on the ground. A man steps out of hiding. Castle recognizes him from a sketch of a guy seen at the farmhouse where they first tracked Alexis. Beckett calls again. She tells Castle that Alexis was the target. This mystery gunman blows away the cell phone. He says that’s how the bad guys are tracking him. He then advises Castle to grab his $3 million before they skedaddle. The stranger says his name is Jackson Hunt (guest star James Brolin). Castle thinks it’s made up identity. Hunt confirms that it is.

At Hunt’s place, Castle sees that he has photos of Alexis from when she was young. He also has a clone of Castle’s phone, though this one is safe to answer. A man named Volkov says he’ll exchange Alexis for Hunt. Castle doesn’t understand until Hunt explains that the person who took his daughter did so to draw him out into the open. He knew he would come looking for her because she’s his granddaughter. Jackson Hunt lets Castle know that he’s his long lost father.

Castle’s dad is a longtime spy who didn’t know he had a son until a year after Castle was born. He never made contact because his dangerous job dictated that he have no relationships. That didn’t stop his dad from giving Castle a copy of Casino Royale when he was 10. It’s the book that made Castle want to become a writer. Castle’s dad also greased some wheels at the CIA when his son was trying to get research info. Little things like that made him feel at least a little bit like a father. He’s been checking in on Castle his entire life. Alexis, too. Now father and son must work together to get her back.

Volkov wants revenge on Hunt for killing his wife. They need to attack this bad man’s compound. Castle communicates via walkie talkie with his dad as he sneaks in to disable the power, but is promptly captured by Volkov’s men. He’s brought upstairs where he sees Alexis being held in a cage. Volkov uses the walkie talkie to call Hunt. He has 10 seconds to give up or he’ll kill his son. Hunt says that’s not going to happen because Volkov is the one who will be dead. The walkie talkie sends out a signal. It’s been rigged. Castle tells Alexis to get down. BOOM! Volkov and his men are killed in a violent blast.

The plan was to have Castle get caught so Hunt could detonate the walkie talkie from afar once it was on the inside. After blowing the lock on the cage, Castle and Alexis escape out the back. They don’t stop until they reach the U.S. Embassy. Before the plan was set in motion, Hunt let his son know that he’s always been proud of him. When Castle and Alexis get back to the States, they are welcomed home by Beckett and Martha. A package arrived while they were in transit. Castle sees that it’s a copy of Casino Royale. It’s his dad’s way of letting him know that he’s still out there. Somewhere.