Three’s a charm, as the saying goes, and Wilton author Mark Rubinstein has capped his Mad Dog thriller series as a trilogy, with a third and final installment just out. Mad Dog Vengeance furthers the story of surgeon Roddy Dolan and his best friend, accountant Danny Burns, left with some unanswered questions following the first book, Mad Dog House and the sequel, Mad Dog Justice.

While his fans asked for more, Rubinstein said new readers can jump right into the third book without having to read the first two, since he offers a quick recapitulation before surging ahead with the final story.

“I never planned to write a trilogy,” he said in an interview at his office last week. “I wrote the first book on a whim. I began getting emails and Twitter and Facebook posts saying, ‘Well, what’s going to happen to Roddy Dolan and Danny Burns next?’

“The first novel ended on an ambiguous note; I hadn’t even thought of the sequel,” he said, but then he embarked on Mad Dog Justice. That book also ended on a very dubious note, resulting in more emails from fans.

“I realized what I really had to do is complete the trilogy, and I brought it full circle,” Rubinstein said. In doing so, he realized Roddy Dolan was the first fictional character in the first novel he ever wrote, and he said, “I was reluctant to give him up.”

Taken together, the three books tell one story. “When you look back, it all seems completely linear, as though it had all been planned in advance, and it wasn’t at all,” Rubinstein said. “It’s like life — you go on through with your life, you don’t necessarily have plans except for maybe what you want to do when you grow up, but when you look back on it all, it all seems linear.”

A tough guy growing up in the Bronx, Roddy Dolan — aka Mad Dog — turns his life around with a stint in the Army and becomes a surgeon. Life is good, but a venture into the restaurant business with Danny goes south in a very bad way and Roddy has to dispatch an enemy in the first book. Their situation gets worse in Mad Dog Justice, as the two are hunted by unknown killers.

Mad Dog Vengeance finds Roddy still reeling from the earlier events and then unwillingly entwined with Italian gangsters at war with the Albanian mob, facing what appears to be an unanswerable dilemma.

In the face of all this mayhem, Rubinstein said, the story is one of love, commitment, family, friendship, dedication, and redemption. “That’s what it really boils down to, because Roddy Dolan has to negotiate these horrendous waves of circumstance that he could never have foreseen. … It became, again without having planned it, it became a novel dealing with life choices, decisions, the psychology and the morality of deciding what you’re going to do and what you can’t do.

“For me, it took on a deeper meaning than just being a story about a guy who finds himself in an impossible situation. … Everything he believes in is put under a microscope, so in a way it relates to all of us, I think, in that we all have to make decisions about what we’re willing to do and not do.”

Rubinstein’s first career was as a psychiatrist, and as such he “spent decades listening to people tell stories.”

“When you boil everything down, psychology is everything,” he said. “What are novels but stories about people in conflict, and conflict is about the psychology of not knowing what to do. Which road should I take? What’s going to be better or worse? Conflict and psychology are basically everything in literature and writing.

“So is murder,” he continued. “The greatest literature is all about murder — Crime and Punishment, Hamlet, you name it. Murder and violence put people into situations that are extreme, and the extremes of life are what make for conflict, horror, a sense of dread, and the question, Oh, my God, what’s going to happen next?

What’s happens next? That’s the essence of storytelling.

Readers enjoy it, he said, “because we live vicariously. Most of us feel our lives are as dull as can be. We look for entertainment — be they on the screen or on the page, or on the TV set, we look for stories in which people are put into extreme circumstances and we identify vicariously with the protagonists of these stories and we always want to know, What happens next?

“That’s a very seductive question. … Every storyteller in whatever medium is involved and engaged in seducing the reader or the viewer, and if you don’t do that, you just have beautiful words on a page that go nowhere.”

From Philip Roth to E.L. Doctorow to Dennis Lehane, “these are literary writers all dealing with death and the unknown,” he said.

In addition to the Mad Dog series, Rubinstein has written several standalone novels, including Love Gone Mad and The Lovers’ Tango. He has also written a number of medical non-fiction books as well as two based on his work as a psychiatrist: Bedlam’s Door: True Tales of Madness and Hope and Beyond Bedlam’s Door: True Tales from the Couch and Courtroom.

Rubinstein is already at work on his next novel, which will be another stand-alone thriller, albeit “more literary.”

C.J. Box, best-selling author of Paradise Valley and Vicious Circle, says, “Mad Dog Vengeance blasts out of the gate and never lets up. Yes, it’s an absolute thriller of a novel. But it’s also smart and humane with a great sense of place.”

Mad Dog Vengeance is published by Thunder Lake Press (thunderlakepress.com).