“Three blind mice. Three blind mice. See how they run…”

Harmless enough, that old nursery rhyme.

But put the name of whodunit playwright Agatha Christie near it and it becomes a bloody frightening tune — and the signature ditty for her longest running murder mystery “The Mousetrap,” which opened Tuesday at Acadia Repertory Theatre in Somesville. Acadia devotees wait all summer for the annual Christie installment. And this year, it has been well worth the wait.

Director Ken Stack is at his best with this type of deadly drama where the lights go out, a group of strangers is stranded, and somebody’s having fun with murder. The setting for “Mousetrap” is an old manor in the inaugural nights as a guest house. The guests file in during a snowstorm, which traps them all in a chilling situation. On the second day, a police sergeant arrives on skis and informs the guests that a murder has been committed in a nearby town, and the investigation has led him to the inn’s address. He searches the house, questions the guests, and stirs up doubts about who’s who and what’s what.

When one of the guests, a persnickety old woman, is found strangled, the danger is heightened. The killer is among the guests, and each one of them has a mysterious background that could point to guilt.

Have you ever seen such a sight in your life, indeed.

This is a deliciously macabre play that keeps you in a roulette wheel of guesswork. The sold-out crowd on opening night was abuzz with accusations during intermission. The youngest audience members led the pack with queries. “It was the cop all the way,” said one teen. “I think it was Christopher Wren. He’s crazy,” said a little boy. “It’s the young girl. Her eyes are big,” said a girl.

In short, this is a creepy good time for sleuths of all ages, thanks to Christie’s fun script and Stack’s sporty direction. This is, by far, the cast’s best work of the season, too. What they lack in actual British mannerism, they make up for twofold in good old American robustness. The highlight performances of the show include Alan Gallant, who is debonair and entertaining as the mysterious Italian charmer Paravicini; Douglas H. Rainey who is terrifically loony as Christopher Wren; and Kathleen Lake who is pluckily cantankerous as Mrs. Boyle.

Siobhan O’Neill as Mollie, Michael Sears as Metcalf, and Keith Tralins as Trotter also turn in good performances. Daniel Vespa as Giles, and Kimberly Horn as Miss Casewell, are somewhat less convincing but don’t at all hold the show back from being amusing, scary and fun.

The set is standard “manor fare” — dark wood, antique furniture, oriental rugs — a la the ever-able set builder Ken Stack. And except for a suit that simply does not fit Alan Gallant or his character, costumes by Rae Johnson are straightforward and pleasant. Two of the actors wear fakey mustaches which are entirely too comical to be believable, but generally the look of this show sets the mood for a night of mystery and mirth.

“The Mousetrap” will be performed 8:15 p.m. Tuesday-Sunday through Aug. 27, and 2 p.m. Aug. 13, 20 and 27 at Acadia Repertory Theatre in Somesville. For tickets, call 1-800-330-7260.