A train carrying a popular Senator is derailed by a car positioned on the tracks. Brennan works out why the dead body of a rich businessman was placed in the car, and the search continues for her father. The team has a new boss.

When the remains of a young pregnant woman and fetus are found in the Delaware Bay and identified as a newlywed who disappeared a year earlier, the investigation is aimed toward her husband, but takes a surprising turn. Booth is upset that his ex-girlfriend is letting their son spend time with her new boyfriend.

When the body of a young man, who's been missing for nearly three weeks, is discovered, the investigation leads them to his girlfriend, who is a foster child. Bones becomes emotionally involved in the case since, she too, became a foster child after her parents disappeared.

After digging up the skeletal remains of a young girl, the investigation points to a convicted serial killer on death row. The team follows cryptic clues that lead to another body, an accomplice, and a victim who may still be alive.

There are two suspects with the same motive when Booth and Brennan investigate the murder of a man found in a bathtub full of chemicals. They soon discover that he had two wives and a girlfriend.

Booth and Brennan investigate a death due to an explosion in a Miami hotel. The clues lead to foreign diplomats with diplomatic immunity.