Robin Pope was not only a cancer survivor, but a loving mother, wife and friend to many. She knew everyone in her close-knit, waterfront community on Chesapeake Bay in Maryland. So there's grave concern one cold night when she goes missing.

Robin Pope was a 51-year-old married woman living with a dangerous secret: she's having a passionate affair with a man who's already engaged to someone else. And Pope has a husband at home demanding answers. Pope's fate remains shrouded in mystery, still the talk of the town in the small community of Stevensville, on the western shore of Kent Island, Maryland.

"We know she was in the water. We know that she drowned," said Maryland State Police Sergeant David Sexton. "We don't know how she got there."

To all outward appearances, Robin Pope was happily married to Wayne Pope, her husband of 22 years. But Priscilla Hastings, Robin's daughter from her first marriage, says her stepfather Wayne had a dark side that she experienced firsthand. She says that even her dog became the target of Wayne's abuse.

In later years Priscilla moved out of the house, but Robin's longtime local friend Debbie O'Malley says Wayne's treatment of Robin went downhill.

"He was very degrading," said O'Malley. "He wasn't physically abusive to her at all. He would say 'You look terrible, you look gross.' He was always that way with her, just say little things to belittle her."

Priscilla says her mom struggled with breast cancer and weight gain from chemotherapy, but rebounded from both, spending hours at the gym.

Robin kept up her job as a dental assistant through it all, and according to friends, kept up her spirits too. But Priscilla says the marriage was in trouble, and that things really came to a head when Wayne found out that Robin was having an affair with her gym instructor.

Sgt. Sexton says Wayne Pope told police he discovered the affair after searching Robin's cellphone, and then locked her out of the house.

But police say Wayne didn't just grab Robin's phone. He reportedly grabbed a gun and headed over to her boyfriend's house that he shared with his fiancée.

"He may have brought a gun to the house. But when he saw the fiancée there he didn't point it at anybody, he didn't pull it from his waistband," said Sexton. Wayne was not arrested. "They asked him to leave and he left, there was no real crime."

According to police and friends, Robin moved into a nearby condo after the separation. The condominium does not allow dogs, and Robin had to leave her Great Dane Bella with Wayne. Three weeks later she went back to Wayne's house under what friends say are mysterious circumstances on the last night she was ever seen alive.

Sgt. Sexton says a phone company technician was working at Robin's condo at the time.

"The technician just remembers her starting to cry, and he was like 'Hey, is everything OK?'" said Sexton. "And she said that, 'Well, my husband just told me that he put down Bella, my dog.' That's when Wayne told her 'No, I didn't put Bella down.'"

Police say Robin texted Wayne that she wanted to stop by and pick up her mail. But Debbie O'Malley believes Robin was deeply worried about Bella as well.

Police traced Robin's path along the Chesapeake Bay Bridge as she drove on a cold late Friday night on the first day of March to Wayne's house. They say she was coming straight from a job interview and dinner in Annapolis, Maryland.

"Through phone records and EZ Pass and tag readers, we know exactly what time she came over. It was about 10:05 in the evening," said Sexton. "And we also know that she was texting and conferring with Wayne, her husband."

March 1, 2013, is the last day any of her friends saw Robin Pope.

An all-out search is launched for Robin Pope. She was last seen at the home of her estranged husband, a guy who police believe is not telling them the whole truth.

Police are left with little to go on after robin's disappearance that night.

In the course of their investigation, they check out Robin's gym instructor boyfriend, who is also in the Air Force, and his fiancée.

"He's a pilot," said Sexton. "We actually spoke to his supervisors and superiors who said Yes, he was in Kansas at the time she went missing." Cops say the fiancée got an solid alibi too.

With that, they turn to Robin's husband Wayne, hoping to find more answers.

"The question is, Why did she want to go over there so late?" said Sexton. "There are a lot of questions about her being alone with him and her not feeling safe around him."

Wayne Pope tells police he spoke with Robin on the phone as she drove to his house. But they say that's where the story gets murky. Because according to Wayne, the very next thing he did was fall asleep with Robin less than 15 minutes away. Wayne told police he woke up about an hour later and went outside to see Robin's car parked in his driveway.

"Goes outside, sees her car there, she's sleeping in the car. He knocks on the window and says 'Hey, if you need to get your stuff then go ahead, get your things, I'm going to my parents,'" said Sgt. Sexton.

And then, police say, Wayne got into his car and drove away.

"He said he's going to his parents' house, and then when we talked to the parents, they said 'We don't recall him being there,'" said Sexton.

Wayne tells police he returned to his house two hours later, only to find Robin's car empty with her purse, keys and phone sitting in the front seat -- Robin are Bella are gone. Wayne says he headed out again to search for her. At some point he is picked up on a store surveillance camera as he stops for coffee.

"He was at 7-Eleven. We have him on video. That was about 1:07 a.m.," said Sexton. Shortly after that Wayne stops at Debbie O'Malley's house.

"He was very distraught," said O'Malley. "He said 'I just don't know where they are. Bella and Robin disappeared. She came to the house. I told her my lawyer thought it would be best if we're not together alone, so I left.'"

Wayne goes to check Robin's condo with Debbie O'Malley's daughter, but comes up empty. They arrive back at O'Malley's house about 2:30, according to O'Malley. She tells Wayne he needs to go home and call the police. And he did.

"One of the first things we listen to, the 911 call, especially from a spouse, anybody, just to find out what their demeanor was, how excited they were -- he was pretty excited about it," said Sexton. "He seemed relatively scared that his wife was missing. It seemed genuine at the time."

The morning after Robin's disappearance, her family and friends and police kick off a massive search for Robin.

A body washes up on shore -- but it's not Robin. It's her beloved Great Dane, Bella, found dead on the rocks near the water, not far from where Robin was last seen, at the home of her estranged husband, Wayne Pope.

"Initially we thought maybe the dog had drowned, but we had an autopsy done by a veterinarian, and the vet basically told us that she believed the dog died of exposure, did have a little water in the windpipe. That's indicating the dog was alive when it went in," said Sgt. Sexton.

And then about two weeks into the search, another haunting clue washes up on shore.

"We were walking along the shoreline and my girlfriend Carol found the shirt in the water, and we pulled it out and it was her shirt," said Robin Pope's friend Debbie O'Malley. Her friends are sure the shirt belongs to Robin.

But there is still no sign of Robin -- until 22 days after her disappearance: a horrific discovery and a major break in the case. Police get a 911 call from a man fishing with his daughter off a pier off Kent Island. They have found a body.

"He looked over and noticed something floating in the water and saw that it was a body over on the shoreline and called 911 right away," said Sgt. Sexton. "We thought it was going to be Robin, and of course it was."

The family gets the autopsy results, but the coroner is unable to explain just how Robin died.

"The only thing they could tell us is that she had water in her lungs and that she probably drowned," said Sexton. "Water in her lungs means she was alive when she went into the water. There's going to be water in their lungs because they're trying to breathe in air and they drown. You can also be in the water two or three weeks and water goes into the lungs because it absorbs the water -- it's a sponge."

Police don't know if Robin was pushed or held under water, but they say at least one piece of evidence indicates that she did not go in voluntarily.

"She was wearing high heels," said Sexton. "For somebody that's wearing high heels, you wouldn't think there would be anybody this close to the rocks.

"All the indications point to us that she was not having any kind of depression," said Sexton. "I don't think she was depressed about the split between her and Wayne, and talking to her family and friends, there were no indications."

Police also rule out Robin's one-time love interest -- her gym instructor -- as a suspect. And they find no witnesses to any foul play.

"I think Robin went in to save the dog," said Sgt. Sexton.

Police say the discovery of Bella and Robin in the same area creates all sorts of scenarios about what happened.

Wayne Pope is not charged with any crime in the death of Robin. But police say he remains the only person of interest in the case.

Later Queen Anne's County State's Attorney Lance Richardson is relieved when Wayne agrees to take a polygraph test.

"If he were specifically asked 'Did you kill Robin Pope?' and he was able to say 'no,' and did not indicate deception, I said 'I will allow you to present that to the public,'" said Richardson. "And I said 'If you fail said polygraph, I will withhold that from the public at this time.'"

But things don't go quite as planned.

"He was there, he was present in the lobby, but before they could get him hooked up and administer the test, he left," said Richardson.

And State Attorney's Chief of Staff Rob Penny says the invitation to the polygraph exam remains open.

Crime Watch Daily tracked down Wayne Pope. He told us that under advice of his attorney, he would not talk to us.

Anyone with information related to the Robin Pope case is asked to contact the Queen Anne’s County Sheriff's Office at (410) 758-0770.