After several days of rain last fall, the sun emerged over Piccadilly Circus, London’s equivalent to Times Square. Double-decker buses chugged along the street and tourists, happy to see a grayless afternoon, strolled along Shaftesbury Avenue. In Cappuccetto, a small patisserie tucked in behind the Palace Theatre, where “Les Miserables” was playing and playing and playing, Marcus Lloyd quietly drank hot cocoa and ate a croissant.

Lloyd, whose thriller “Dead Certain” opens Friday at Penobscot Theatre in Bangor, grew up in London and, in an unusual move for a young man who would eventually become a playwright, studied physics at Oxford University.

“I wanted to find out how the universe was put together, how it works,” said Lloyd, who is soft-spoken and sweet-faced in a way that belies the fact that he is nearly 40. “But I always knew I would not go into physics.”

One big clue about the direction his professional life would take was the diary he began keeping at age 15. “It is the most precious thing,” he said, in a tone that makes it clear that, in a fire, he would grab the diaries first if he had to evacuate quickly.

In a more determined way, Lloyd’s career began to take shape when he enrolled in a local playwriting class taught by the English dramatist and novelist Bernard Kops. In class, Lloyd’s scenes were read out loud, and Kops must have realized a young artist was in the making. To that end, the teacher assisted in delivering one of Lloyd’s plays into the hands of an agent.

“I thought to myself: If this doesn’t work, what will I do?” said Lloyd. “I based all my hopes on this working, and fortunately, it went very well.”

Eventually, Lloyd won a scriptwriting contest through the British Broadcasting Corp. and began writing radio plays. That’s when the outline of “Dead Certain” began to form in his thoughts.

It is the story of a wheelchair-bound former dancer who hires an actor to come to her home to

coach her in performance technique. As the plot thickens, the audience learns of an ulterior motive and a possible murder scheme. But to give the rest away would be suspense-genre blasphemy.

“I’ve always been fascinated by the question of ‘How much control do we have over our lives?'” said Lloyd. “Are we following some script out there, or do we have some control? Physics deals with that. But I also wanted to deal with the question of ‘Are we responsible?'”

The interplay of destiny and freewill appealed to Penobscot’s artistic director, Mark Torres, because of the intelligence of the drama. It’s likely he was also drawn to the economical two-person cast, in this case Broadway actors Matt Edwards and Rita Rehn (who appeared in Penobscot Theatre’s 2002 production of “Betrayal”).

“It reminds me a little bit of ‘Sleuth,’ but only because it has two actors,” said Torres, who has also directed local productions of the classic thrillers “Wait Until Dark” and “Dial M for Murder.” “I thought it sounded like a good thriller. When I read it, it lived up to that expectation. The experience of a thriller is a strange one. We read a Stephen King novel because we have the pants scared off of us. ‘Dead Certain’ has the same quality of experience. You’ll be dragged through some harrowing stuff. For some reason, we love that.”

Indeed, Lloyd was a young teen when he saw Anthony Shaffer’s mystery thriller “Sleuth,” about a man who sets up his wife’s lover for a deadly game. “I thought it was fantastic,” Lloyd said. “It gripped me and stayed with me always as a very exciting event.” Later in life, Lloyd fell in love with a dancer – his American girlfriend Candy Veal, with whom he lives – and while the story isn’t autobiographical, the writer had the perfect circumstances at home to facilitate an imaginative and terrifying variation on a theme.

“Dead Certain” was originally staged after Lloyd entered a contest and lost. One of the judges, however, called him on the phone and said he wanted to help get the play produced. The world premiere took place in 1999 at the Theatre Royal in Windsor, England. Since then, it has been produced in New Zealand, again in England, and twice in America – in California and Long Island, N.Y.

The Penobscot production, for which Lloyd and Veal are traveling from London, is the New England premiere.

“I’m very excited about it being in Maine,” he said.

But the excitement – the chills and thrills – Torres hopes, have just begun.

Penobscot Theatre will present “Dead Certain,” by Marcus Lloyd, April 23-May 2 at the Opera House in Bangor. Tickets are $12-$25. Lloyd will participate in a post-show artistic director’s forum immediately following performances at 5 p.m. April 24 and 2 p.m. April 25. For more information, call 942-3333.