Just Passing Through
In the wake of Charlotte identifying Dave as her killer, Nathan interrogates him to get the truth. Croatoan was possessing Dave at the time so he doesn't remember anything. Though under Nathan's pressure, Dave recalls a time once before when he "lost time." That one time in 1983 when he woke up on the beach next to Lucy and Nathan's dead son, James AKA "The Colorado Kid". The details from that day are foggy, but Dave does remember seeing a woman disappear in and out of a thinny. Without much else to go on, Nathan focuses his energy on this single fact and from this, he realizes that there's another way into The Void and...from this he realizes that there's another way to get the "controller" Charlotte said they needed in addition to the aether core to build a new Barn.
Later, Audrey and Nathan take a walk on that same beach where their son was killed years ago and Nathan explains everything to Audrey but she isn't sold on it all just yet. She can't sense or see a thinny anywhere around them on the beach, so how are they going to find some mystery woman from 1983 who could create thinnies? By going back in time to 1983 to talk to her of course.
Nathan prepares for his trip back in time by raiding Good Will for a Members Only jacket and by activating Stuart Mosley's, who once sent him back to 1955, Trouble. Whenever Stuart sees Nathan and a specific portrait of his family he gets agitated and creates time travel magic, depending on how you look at it. Vince, for his part, prepares to not look out of place in 1983 by pulling his hair back into a pony tail. Smooth.
Once they're back in 1983, Nathan posses as FBI agent Nathan Butterworth and shows his dad, Chief Wuornous, a sketch of the mystery woman Dave saw jump in and out of a thinny. Lucy, Audrey's 80's persona, immediately recognizes the sketch as Barbara Colton, who's Trouble allows her to phase in and out of solid mass (i.e. gates, walls, doors etc.), just like Hailie. On a side note: Lucy and Nathan's dad are in a relationship, which means that Nathan unknowingly had a baby with "Sarah" in the 1950s, which would later be his stepmother, "Lucy" who would then become the love of his live "Audrey". Hmmm. Oh and in this timeline of events Lucy is preparing to go into The Barn for her 27 year stint and she's emotional about having to say goodbye to her son James.
Now, back to the plot. Nathan blows his own cover when he refers to a local hospital as "The Ping", a term that only Haven PD cops use. Lucy also finds him snooping around Garland's office for Barbara Colton's address, which he finds. Lucy able to tip Barbara off that someone is looking for her, thinking that Nathan has some ulterior motive to hurt Barbara because she's Troubled. In the midst of all this, Lucy also manages to notice how cute Nathan is, but he might be a bad guy and she's also dating Garland and this is only an hour long show so there's no time to act on any feels at the moment. When Nathan gets to Barbara's house, Nathan notices that she's wearing one of the rings from Charlotte/Mara's dimension. Before he can stop her, Barbara creates a thinnie and hightails it out of her house. Garland shows up ready to shoot "Nathan Butterworth" so Nathan has to come clean that he's actually his son.
Meanwhile, Vince breaks his promise to Nathan to not try and change past events by doing exactly that. Vince tries to lure the younger version of Dave out of town under the premise that Vince is a big shot literary agent who wants to hire Dave to cover a story in New Mexico. This elaborate tale isn't far fetched at all, so we're not sure why Dave didn't take the bait (that's sarcasm in case you missed it) and instead figured out that it was in fact his brother Vince from the future!
With the jig officially up on all fronts, Vince spills the beans about Croatoan and what's going to happen to Dave later on in the day if he doesn't get out of town immediately. Dave agrees to flee, until he gets an impromptu visit from Lucy who's there to borrow Dave's gun. You see, Lucy stopped by Barbara Colton's house to find out what info Garland was able to round up on "Nathan Butterworth", but she walked in midway through the two Wuornos men's conversation and overheard Garland telling Nathan that agent Howard says that if Lucy kills the one she loves the most – her son James – the Troubles will go away forever. Off this devastating information, Lucy then goes to Dave to ask for a gun because it's a tough call, but she's prepared to kill her son for the greater good of saving Haven. Dave is really touched and inspired by it all and decides that he isn't going to run from his fate or from Croatoan.
Fast forward to the beach, just as an understandably rattled Lucy is about to shoot her son James in the back when Nathan stops her and tells her that he's James' dad, he's from the future, and she can't kill their son because Dave has to. Lucy doesn't have a lot of time to process it all or to ask questions because the next chain of events happens really fast ...Garland shows up chasing Barbara Colton who creates and hops into a thinny and hops out on the other side to escape him. The open door (thinny) to The Void lures Dave in and before Vince can grab a hold of him, Croatoan possesses Dave. Under Croatoan's influence, Dave sucks all the life and aether out of James and then wipes the memories of everyone on the beach. Croatoan exists the scene by disappearing back into The Void, leaving Dave to pass out next to James, all while Lucy and Nathan watch the entire scene unfold unable to change the events of the present for the sake of the future. When Dave comes to, he can't recall anything that happened – he lost time.
With more insight about how this significant event in the past has effected their present, Nathan and Vince hitch a ride back to the future by finding 1983 Stuart Mosley and showing him the photograph that triggers his Trouble.
Everything ties neatly together when we land on Duke, who's still on the outskirts of Haven, holed up in a motel room with some thugs who are keeping him captive until "The Boss" gets there. If this were a mob movie, Duke would be sleeping with the fishes by the end of the credits, but since it's not, "The Boss" was actually Saul Goodwin, a little boy Nathan met back in 1983 at the Haven police station. Saul, who worked for the school newspaper as a kid, was also the one who captured the iconic "Colorado Kid" photo that depicts James' murder scene on the beach that no one can seem to remember the full details of, thanks to Croatoan. Back in 1983, Nathan handed young Saul a letter to deliver to Duke when the time came years ahead in the future, so Saul has been following Duke all these years waiting for the right time to make good on his promise to Nathan (granted, he can't remember Haven thanks to the Trouble making everyone forget it, but he's got the note with his instructions).
In the letter, Nathan explains to Duke that to get back into The Void, they need a member of the Colton family to use their Trouble to create a thinny so that Nathan can travel between dimensions to get the controller they need to make the new Barn, which will end the Troubles once and for all. But since Barbara Colton peaced out to who knows where, Hailie Colton, the last surviving member of the Colton family and who Duke tried to kill a few episodes back, is their last hope. If Duke can bring her back to Haven with him, the town may have one last shot at survival.