As Jack Carter plans a surprise party for Zoe's 16th birthday, his ex-wife and Zoe's mom, Dr. Abby Carter, strides into his office. She reminds Jack that they made a deal: Zoe could live with Jack for one year, after which she would return to live with Abby. Jack urges Abby to reconsider, confessing that he's never even told Zoe about this arrangement. Abby holds firm. A year has passed, and she is determined to take Zoe home with her.
Jack needs to persuade Abby that he's a great dad who no longer puts work ahead of family. Unfortunately for him, his work happens to be really, really important today. Weird weather is plaguing the town, and after a man turns up frozen solid in a hot spring at Eureka's exclusive spa, Jack must investigate. Working with Henry, he learns that the spring's temperature somehow plummeted to –460 degrees Fahrenheit and instantly froze the victim: Neil Baxter, a womanizing scientist at Global Dynamics.
As Jack checks out Baxter's research, battles bizarre weather, and completely fails to explain the custody deal to Zoe in a calm, reasonable way that doesn't freak her out, his friends are also busy. Henry wins the job he wants at Global, while Allison receives an anonymous e-mail claiming that her son Kevin has been the subject of experiments involving Stark's mysterious artifact.
Pete Puhlman, the Eureka Channel's meteorologist, tells Jack that the drastic freeze at the hot spring has destabilized the local climate, causing the worsening weather. Lupo then discovers that another meteorologist, Steven Whiticus, owns a cabin near the spring. When Jack visits the cabin, he finds a massive satellite that can only be, in his words, a "crazy weather machine." Lupo adds the clincher: Steven's wife Wendy was having an affair with Baxter.
Believing that they have found their murderer, Jack and Lupo move to arrest Steven. Wendy, however, reveals that an eye injury forbids her husband from ever leaving his house in town. Steven then adds that he approved of the affair because of the happiness it brought Wendy. Jack and Lupo are flummoxed.
All along, the weather has been growing more dangerous. Now, as huge hailstones and hurricane-force winds threaten to tear the town apart, Jack must find the real culprit and figure out how to reverse this meteorological nightmare. If he succeeds, he must then resolve the custody question with Abby and Zoe.
The first challenge might kill him. The second might break his heart.