Dana comes to ADA Gabriel Lowan, requesting help on a case. He calls in Catherine and her partner, Tess Vargas. Dana is tracking a group of thieves. One of the members figured out Dana was following her, and tried to kill her. Dana shot back, and killed the thief, Mara. Dana asks Catherine to go undercover in place of Mara in order to find out what the thieves are after. When Gabe questions why she's chosen Catherine, Dana reveals she knows about Catherine's father, FBI Agent Robert Reynolds, who was recently sent to jail by Gabe, Catherine, and Tess; she feels like she can trust them if Catherine is willing to put her own father in jail. Though Gabe thinks it's too dangerous, Catherine agrees to help.
Catherine infiltrates the group and finds out they're after a gem that is being kept in a safe at the Russian consulate. Dana realizes that Gabe likes Catherine more than he lets on. Meanwhile, Catherine is unsuccessful at retrieving the gem, claiming it was stolen before they could get to the safe. Dana suspects that Catherine is hiding something, and reveals that both she & Catherine have a personal connection to the gem. Dana's husband, Sam, was killed six years ago while helping her out on a case, and his murder is connected to the gem. Dana also reveals that the gem was linked to a murder in London in 1836, and Scotland Yard was assisted in the investigation by Rebecca Reynolds, Catherine's ancestor.
Dana later notices the same gem being worn by Tori Windsor in a magazine, and tells Tess & Catherine to arrest her. They bring her in, but the entire precinct is taken hostage by a group of thieves who are after the gem. When Vincent Keller comes in to rescue them, Dana suspects that Catherine, Tori, and the rest of the group are hiding something. The hostages are all rescued, but Dana is convinced that there is more to the story than Catherine & Tess are letting on.
Dana is later shown doing surveillance on Vincent's house. She sneaks in while Vincent is out, but is caught by Tori, who ties her up. Vincent comes back, and releases her, angry at Tori for tying up an FBI Agent. The two get into an argument, and Dana sees Tori partially transform. She finds out Vincent & Tori's secret about being beasts, and that the gem the thieves were after is able to control beasts. Vincent asks Dana to work with him to find the gem before somebody uses it against him; Dana agrees, wanting to find Sam's killer. Catherine & Gabe come by, and reveal that Vincent's best friend, J.T. Forbes, has been kidnapped by whoever stole the gem. Dana helps Tess direct Catherine & Gabe, using notes from Rebecca's file, to an abandoned building owned by Tony Barnes. They're able to rescue J.T., though Tori dies trying to save him.
At the precinct, Tess & Dana find out that "Tony Barnes," the man who kidnapped J.T., is actually Frank Darnell, a professional con artist. They go to interview the other hostage found with J.T., and Dana recognizes him as Sam, and the two reunite.
Catherine goes to meet Sam & Dana afterwards, and finds out they had a son, Adam, who died from leukemia right before Sam disappeared. Sam invites Catherine to come for his & Dana's vow renewal on Valentine's Day, but she reveals that she already has plans with Gabe.
After Sam is attacked by a mysterious invader, he gets Catherine & Vincent to agree to come to the vow renewal to protect them. At the vow renewal, Dana & Sam come with Catherine, Vincent, J.T., and Tess. Later, though, Gabe shows up, wanting to talk to Sam. After they leave, Vincent reveals that there's a bomb under the chapel, and they need to leave. After the bomb explodes, Catherine reveals to Dana that Sam is actually the mastermind conspiring with Frank, and was responsible for kidnapping J.T. and killing Tori. Dana realizes Sam is no longer the man she knew, and agrees to Catherine's offer to go into witness protection, letting Sam believe she's dead.
Dana is mentioned by Agent Knox, though not seen on-screen. When Agent Knox tries to rescue Agent Mallory from a group of terrorists, Dana suggests that he get Vincent's help. Vincent is a fugitive wanted for murder by then, and Dana tells Knox to find Catherine first.