After Safety Inspector Butch Hicks falls to his death off an offshore oil rig, Chief Vick enlists Shawn and Gus' help with the case. As she takes them out to the crime scene on the police boat, she tells them they received an anonymous tip that something highly unsafe was happening on the rig and the caller was risking his life to warn them. When Shawn and Gus ask why she didn't enlist help from her detectives or the Coast Guard, she tells them they are working more in an unofficial capacity. Just then, they are pulled over by the Coast Guard, whose commander, Barbara Dunbar, questions Vick's authority over the Hicks case. As they are arguing over jurisdictional lines, Shawn realizes they are sisters.
After a judge determines that Barbara and the Coast Guard have jurisdiction, Barbara co-opts her sister's chief psychic to work for her, a move that annoys Vick. But when Shawn and Gus show up at the dock to take the boat to the rig with Barbara, they get word that she wants them to stay put and do nothing. Barbara doesn't want their help, she just wanted to take something away from Vick. Not to be swayed, Shawn and Gus hop a ride out with rig owner, Billy Joe Bamford and his daughter Ashley. They initially tell them they are potential investors but then quickly come clean as to the real reason they need onto the rig. Billy Joe tells them that if Hicks' death was in fact a murder, he'll do what he can to help. He shows them around the rig, passing the locked office of a geologist Ashley hired to help them assess where to drill - help that the wildcat Billy Joe doesn't feel they need. As Billy Joe lets them into Hicks' office, Shawn spots a map on the wall detailing the location of the rig. Inside the office, they find evidence that suggests Hicks was the one who called in the anonymous tip to the cops. Barbara shows up and tells them that even if that was the case, it still doesn't point to murder. She tells them they need to be on the next shuttle off the rig, which leaves in an hour. Shawn figures that gives them an hour to investigate. They interview the crew that was working when Hicks died. It turns out everyone hated him because he was such a stickler for the rules, which means he should have known better than to go into no man's land - an unsafe area of the rig that is off limits to personnel - which is where he died. Shawn and Gus decide to go to Hicks' house to look for hard evidence.
They stop at the police station to get help gaining access to Hicks' house. Lassiter and Juliet are hard at work on a missing person's case, a university professor named Renaud, and Vick, still stung by their defection, is in no mood to help, either. But she softens when Shawn tells her he only agreed to work with Barbara to get evidence that will bring the case back under Vick's jurisdiction. At Hicks' house, Shawn and Gus find emails from someone threatening to go to the authorities. They realize this person, not Hicks, was the anonymous tipster. They also find the dead body of Professor Renaud, Lassiter and Juliet's missing person. Shawn and Gus call both the cops and the Coast Guard to the house, where they tell them that Renaud was the geologist Ashley Bamford hired. He worked on the rig with Hicks and was the anonymous tipster. He discovered something unsafe and was emailing Hicks about it, who then killed Renaud to keep it secret. Both Vick and Barbara thank them for their help but say they will each take it from there. Shawn and Gus decide to get back to the rig on their own to see if they can find out just what Renaud had discovered.
Back at the police station, Barbara goes to see Vick and tells her that the Coast Guard discovered someone had tampered with the crane that got loose and killed Hicks. Shawn was right, Hicks was murdered. Vick tells her Shawn was also right that Hicks killed Renaud. Putting their differences aside, they decide to find Shawn together to see what else he knows. But he and Gus are already on the rig, where they break into Renaud's office and discover evidence that, contrary to the map they saw earlier, the rig is located directly on a fault line. Ashley finds them and they warn her that her father made fake maps and is drilling on a fault line. Also, he may be involved in the deaths of Hicks and Renaud. But it turns out that Ashley is the real culprit, and she turns the tables on them, locking them in a closet to make her escape. As she heads off the rig, she runs into the cops and Barbara, who have just arrived. They tell her they found out she was on the rig the night of Hicks' death but kept her name of the manifest. Ashley then pulls a gun on them and takes off running. Lassiter, Juliet, Vick and Barbara give chase. Lassiter and Juliet find Shawn and Gus and let them out. A gunfight ensues as they all then track down and corner Ashley, but Shawn, telling her he understands what it's like trying to live up to a father's expectations, is able to talk her down and disarm her without anyone getting hurt. With the case wrapped up, everything goes back to normal, including Vick's relationship with Barbara. The rivalry is back on, she tells Shawn and Gus, and she's winning.