Denny Cutler’s (Kai Bradbury) arrival was the cliffhanger of Season Three of “Virgin River.” He shows up on Doc Mullins’ (Tim Matheson) doorstep with a revelation: He is Doc’s grandson.

The catch? Doc didn’t know he had a grandson — or a child at all. Doc and his wife, Hope (Annette O’Toole), have no children.

Season Four of “Virgin River,” which dropped on July 20, dives into Denny’s backstory and hints at his future, which has a twist of its own. At first, Denny’s behavior seems a bit suspicious — but all is revealed in time.

Below, we’ll unspool all of Denny’s secrets, which are sure to be explored more in Season Five.

Denny is an orphan, but his dad was Doc’s son
When Denny finally catches up with Doc, he asks him about a woman named Rose Miller. Doc’s eyes light up with recognition: Rose was Doc’s girlfriend back in college.

She got pregnant and never told Doc that he was a father, which is why Doc was confused by Denny’s arrival.

Both of Denny’s parents have died due to circumstances that aren’t revealed (but are hinted at, perhaps, later in the season). The death of his parents prompts Denny to seek out his closest remaining living relative: Doc.

No, he’s not stealing klonopin from Doc — but he is planning something
None of the characters on “Virgin River” quite know what to make of Denny. Lizzy (Sarah Dugdale) is confused by his hot-and-cold behavior: He seems romantically interested, then pulls back. He won’t even act in a play at the Renaissance fair with her!

In Episode Five, Denny’s behavior adds up to a big ‘ol red flag for many of the characters. Mel Monroe (Alexandra Breckinridge) catches him breaking into the medicine cabinet of the clinic and taking Clonazepam (better known by its brand name, klonopin).

Essentially, everyone seems to assume the worst in Denny — especially Muriel, who knows someone whose niece made a surprise visit and scammed her out of money. And admit it: You probably began to suspect Denny, too, didn’t you?

Turns out Denny’s intentions are good. He’s using the insurance payoff from his father’s death to pay off debt on Doc’s clinic.

Kai Bradbury as Denny Cutler (L) and Sarah Dugdale as Lizzie (R) in Virgin River. (COURTESY OF NETFLIX / COURTESY OF NETFLIX)
Kai Bradbury as Denny Cutler (L) and Sarah Dugdale as Lizzie (R) in Virgin River. (COURTESY OF NETFLIX / COURTESY OF NETFLIX)
Denny has a degenerative hereditary condition called Huntington’s Disease
In the finale, we learn one last secret that explains some of Denny’s behavior, especially as far as Lizzy’s concerned.

Denny has a degenerative condition called Huntington’s Disease which causes a progressive breakdown in nerve cells in the brain. According to the Huntington’s Disease Society of America (HDSA), the disease “causes deterioration in a person’s physical, mental, and emotional abilities,” and has no cure.

Huntington’s Disease is passed down genetically — which may explain what happened to Denny’s father. According to the HDSA, children of a parent with Huntington’s Disease have a 50% chance of inheriting the disease.

This explains the theft from Doc’s medicine cabinet: Denny used his father’s klonopin to mitigate his own symptoms, which tend to appear in adulthood, and worsen over the course of 10 to 25 years.

Given his condition, Denny doesn’t feel he has a future with Lizzy. In Season Five, we’ll likely see how the two approach their connection.