S4, E23: Booth’s detective friend, Ken Nakamura, calls him from Tokyo in a panic when his sister Sachi goes missing in Washington. Booth and Brennan are on the case, and their investigation leads them to a canal where they find Sachi’s decapitated head. Booth and Brennan meet up with Ken and trace his sister’s life away from home, and their investigation leads them to an elite escort service. When they discover that her roommate is also missing, they must race against the clock to find Sachi’s killer.