After giving us brief flashes of Audrey Parker's past lives, this week's episode of Haven took us all the way back to the year 1955, where we get to meet the redheaded Sarah in the flesh. But when Nathan and Duke find themselves trapped in the sock hop era, they have to be careful not to change the timeline—and they have to preserve it by killing Duke's granddad.

Duke is looking through the memorabilia of his good old homicidal dad when he comes across the name Stuart Mosley in his pop's diary. He heads over to Walter's house, where he makes a rather unpleasant discovery: Stuart's Trouble is that he causes people to travel through time when he's panicked. Stuart recognizes Duke and zaps him back to the year 1955. Duke, being a magnet for trouble with a lowercase T as well as a capital letter, quickly witnesses a brawl between soldiers at a local bar and steps in before the bartender is accidentally killed. Once he realizes what year it is, Duke figures out how to get a message to Audrey.

Meanwhile, in 2012 Haven, Nathan and Audrey are walking down the street when Audrey notices that the newspaper has been shut down and replaced by a comic book store. Nathan reminds Audrey that the paper hasn't operated since Dave killed Vince 15 years ago. Audrey naturally realizes that reality has been altered, and back at the police station, she receives a letter from Duke that has been held at the mail offices since 1955. Following the information in the letter, Nathan and Audrey visit Stuart, who panics again upon seeing Nathan and zaps him back to 1955 as well. Nathan quickly finds Duke and tells him that the timeline has been altered. Duke insists, in a sheepish, I-can't-believe-I'm-saying-this way that he followed "the time travel rules" and has kept a low profile. Then he remembers the bartender, who turns out to be Roy Crocker, Duke's grandfather—a man who was killed by Sarah.

Nathan goes off and finds Stuart, who turns out to be a traumatized veteran. When his platoon was in danger, Stuart zapped them a year into the future, and he can't resolve that impossibility. And Stuart's nurse? None other than Sarah herself. Nathan is, of course, totally charmed by this version of Audrey, who talks like the girl Friday of a screwball comedy, and responds to Nathan's bothering of Stuart by hauling him out of the hospital by the ear.

This episode is titled "Sarah," but it could have easily been called, "The Grandfather Non-Paradox." We don't actually learn that much about Sarah because, at this point in Haven's history, Sarah doesn't know much about herself. She's been given the memories of a badass wartime nurse, and she's eager to help people. But while Nathan is canoodling with Sarah and Duke is learning that his grandfather really didn't want to kill Troubled people, everything is going to Hell in present-day Haven. Apparently, the law of concurrent parallel time passage is in effect, because the Haven timeline is changing. Audrey is a wanted fugitive for killing Reverend Driscoll and Nathan is dead—Chief Wuornos, however, is still alive.

It's not clear what the purpose of the alternate timeline is; we don't really learn anything from it, and from everything else that happens in this episode, the alternate timeline shouldn't be an issue at all. The causality of this episode is actually quite neatly circular: Stuart sends Duke and Nathan back in time because he met them in the past. Duke gives Roy the gold doubloon that Duke received from his own father. Roy dies at Sarah's hands precisely because Duke and Nathan go back in time, not despite it. But then again, I suppose Duke and Nathan wouldn't be so intent on preserving the timeline unless Nathan knew the timeline was changing back in the present.

Eventually, a showdown between Roy and Sarah results in Sarah shooting and killing Roy, and when Duke absorbs Roy's blood, we learn something new about the Crockers: they're definitely Troubled. This isn't a huge revelation, but it does dampen the Us vs. Them quality the Crockers and the other Troubled have historically had in Haven. Afterward, Sarah manages to sooth Stuart into a state of mind that lets him send Duke and Nathan back to the present, saving alternate-timeline Audrey from an execution at the hand of Driscoll's men.

As we flash back to 1955 and Sarah, we do learn one more significant fact about the Haven mythos. Sarah reports to her superior, telling him that she wants to stay in Haven—a superior who bears an uncanny resemblance to the fake Agent Howard. It appears Audrey isn't the only immortal kicking around this town.