Booth and the rest of the lab desperately search for Brennan who was kidnapped by her former assistant, Zack Addy. Brennan's rescue is, however, just the beginning of their problems.

After discovering the body of a man involved with creating artificial intelligence bots, the team must figure out whether the victim's own A.I. bot was programmed to kill him. In the meantime, Bones plans a special surprise for everyone for her 40th birthday.

When the body of an old man is found in an acid dump site, the team becomes enmeshed in retirement home drama. As they explore the case, talk of marriage and kids begins to dominate the conversation back at the lab.

The team investigates the murder of someone from Booth and Brennan's past. Meanwhile, Aubrey faces a moral dilemma of his own when he discovers his dad is back in the picture.

When a tutor of privileged students turns up dead, the team sorts through all the possible perpetrators, from disgruntled parents to the tutor's roommate with a criminal record. Meanwhile, Bones is frustrated with the voice of her audio book and tries to prove that she can record it herself.

The dismembered body of successful golfer-turned-lumberjack Phyllis Paul brings the squints to the Lumber Sports Regional Championships. At this competition, Booth and Brennan discover numerous secrets that could have resulted in Phyllis' murder, including an affair with a married rival. Meanwhile, Hodgins secretly analyzes the bacteria on the bone of a prior victim that he believes will exonerate Zack.

When a series of corpses with ties to Booth's former Army unit appear around D.C., Booth must dive into his past to find the killer before the killer finds Booth. Meanwhile, Brennan's father, Max, hides a serious medical procedure from Brennan, leaving her to grapple with her father's trust and mortality, as well as her family being in danger.

A recent loss creates a rift between Booth and Brennan, as they deal with their grief in different ways. Meanwhile, an old flame from Brennan's past comes to visit.

When a young man dies in a horrendous hay baler accident, Booth, Brennan and Aubrey slap on trashy disguises and go undercover at a rowdy demolition derby competition to investigate the case. Meanwhile, Dr. Gordon Wyatt returns and assists Hodgins and Cam when the ongoing Gormogon case hits a dead end.

Brennan testifies for Zach in trial, Angela reveals some big news, while Aubrey and Jessica come to terms about their future together. All the while, the team discovers Kovac has escaped, leaving Booth in a race against the clock to protect himself and those closest to him from what may be Kovac's most dangerous plan yet.

With Kovac still at large, the team searches for evidence to track him down. After Brennan experiences a setback, the rest of the team must figure out how to find Kovac without her, putting everything she has ever taught them to the test. When all signs point to Kovac having outside help, as well as a hideout, Booth and Brennan go searching for him.