Duke and Audrey first met when she was Lucy and they were photographed together at the scene of the Colorado Kid. Lucy gave Duke her locket which he kept years later, but he never remembered the incident.
Audrey and Duke met when Duke saved Audrey's life after she was thrown into the water while unconscious. Audrey later returns the favour by getting him out of jail. Audrey later repays Duke for saving her by letting him go when Nathan is questioning him. In Harmony, Duke helps Audrey with a sick Nathan, doing her a favour by keeping Nathan on his boat. When Nathan wakes up, he calls Audrey. When they are looking for Ray McBeen's boat, Duke uses this as leverage to come along, which Audrey doesn't want, but Duke insists that he wants to know what the hell is going on. Although it doesn't work as Duke planned as Audrey constantly tells him to stay by the car.
In Consumed, Audrey does by the docks to talk to Duke about Lucy, but Duke is with a client, and comments to Audrey he doesn't talk to cop, even the one he likes. In Ball and Chain, Duke invites Audrey over for dinner and tell her not to cancel. Audrey later cancels the dinner date to pursue a lead, and Duke ends up alone at the Grey Gull, where he meets Helena and they spend the night together. When Audrey figures out what happened to Duke, she works with all her might to help him. When she solves the trouble, she shows him a picture of his daughter she took with her phone.
In As You Were, Duke brings Audrey to her surprise birthday party at a hotel on an island. After the chameleon incident, Duke gives Audrey his present of Lucy's Locket, revealing he was the kid in the photo. In The Hand You're Dealt, Duke and Audrey look up his old babysitter Vanessa Stanley, who might remember something about the photo. In The Trial of Audrey Parker, Audrey is on the Cape Rouge at Duke's poker night when they are held hostage by Ezra Colbert and Tobias Blaine. When they free themselves, Audrey and Duke work together to get the jump on them by Audrey telling Duke what to do so Erza can't read his mind.
In Spiral, Duke notices that Max Hansen can't feel anything, making the connection that he might be Nathan's biological father and attempts to tell Audrey about it. After Audrey meets with Hansen, she meets with Duke and tells her about the hot coffee that that spilled on Max. Audrey and Duke visit Max's former cell mate, Leo, who tells them how Max could take a punch like he couldn't feel it. Duke soon asks Audrey why she was holed up in her room, and she replies she will tell him after she tells Nathan.
In 301, Duke is worried about Audrey when he hears she had been abducted. He helps Nathan look for her and he is the first one to find her inside the Inn she was being held at. In Magic Hour when in Colorado looking for more information on the Colorado Kid, Duke and Audrey kiss. But Audrey stops it before it can go any farther. In Thanks For The Memories before Audrey can enter The Barn she tells Duke that they will always have Colorado and kisses him on the cheek before making him promise not to let Nathan stop her. Duke admits to Nathan that he's in love with Audrey too.
Since Audrey went into the barn and it spat Duke out, Duke begins searching for Audrey with Jennifer's help. He is relieved to see her alive in Lost and Found when she comes out of the Barn. In The New Girl, Duke convinces the Guard to let Nathan and Lexie free so Lexie could fall for Nathan again to stop the troubles. He gets possessed by Tyler, and Lexie lets "Duke" kill Tyler's body and Duke's trouble kicks in. This makes Duke realise that Lexie is actually Audrey and confronts her about it. She confirms it with a "dammit Duke", and hugs him. The next day, Audrey makes Duke promise he won't tell Nathan about her truth identity. First Duke disagrees but then he gives in and helps Audrey to keep her identity a secret.
When Audrey learns in When the Bough Breaks how to give a trouble, he is the first to warn her not to give in to William or her original self, because once Mara broke through, she might not be able to resist and, due to Mara's influence, might not even want it. Later in the episode, Audrey gives him on his request his family curse back. During this, Duke can feel that she can remember who she once was and is concerned that she might turn back into her original self.
Duke doesn't know if they can get Audrey back. Duke believes Audrey is gone and doesn't believe Nathan when Nathan tells him Audrey is still there in Spotlight. Mara tries to use Audrey's connection to Duke to get what she wants, but he resists. In Much Ado About Mara, when Mara is helping Duke release a trouble, Audrey emerges in front of Duke, making Duke realise that Audrey is still inside Mara. With this knowledge, he helps Nathan and Dwight bring Audrey back for a minute.
When Duke returns in Close to Home, Audrey is angry with Duke for leaving them in Haven. However she later forgives him. After returning to Haven, Duke starts to become controlled by Croatoan. This is first shown in Blindspot when he starts to kill people protecting Audrey in the police station. He kidnaps Audrey and takes her to her father, Croatoan. Duke kills troubled people in order to gain more troubles for Croatoan. He also uses Dwight's daughter for leverage in getting something for Croatoan. Audrey coaxes the real Duke back, and he hates what he has done. In a heroic effort to stop Croatoan, he convinces his friends that the only way to stop Croatoan from getting his troubles is for Audrey and Nathan to kill him. They all reject but then he starts leaking troubles, so Nathan grabs him by the mouth and nose and suffocates him. All while Audrey told him they loved him and Nathan says you are the bravest man I’ve ever met.