Each summer, the Elm Shakespeare Company presents a play al fresco. Now in its 17th season, the company has chosen “Macbeth.” On Wednesday night, a crowd gathered in front of a substantial stage in Edgerton Park. They brought their blankets and their picnics and their babies, enjoying the last bit of sunshine on a summer evening.

With a sudden clap of thunder, the play began. Just as shadows crept across the park, the play’s plot twisted towards its darker themes. The audience watched as Macbeth, a Scottish lord, wrestled with his political ambitions and psychological burdens.

The elements of the play amplified the slightly spooky aspects of a city park at night. Spotlights illuminated the rocky outline of a castle, leaving the surrounding area obscured. Perhaps purposeful, the park’s giant trees became battlements and the Big Dipper, directly behind the stage, seemed a faint and far off banner. Most likely coincidental, a flock of crows swept overhead as the voices of the three witches carried across the sky, “Fair is foul and foul is fair: Hover through the fog and filthy air.”

The actors ranged from professional to amateur. James Andreassi, the founder of the Elm Shakespeare Company, plays the leading role, as well as serving as the show’s artistic director. He is also an associate fellow of Calhoun College. Marianna Bassham, who stars as Lady Macbeth, recently played Becky in the Wes Anderson’s latest film, “Moonrise Kingdom.” On the other hand, local high school students, the show’s “Elm Scholars,” acted in a few minor roles.

Although this performance was mainly a traditional interpretation of the play, many of the characters gave Shakespeare’s words a modern inflection. When an owl’s shriek scares Lady Macbeth after her husband’s crime, Bassham let out an audible “phew!”

Bassham shined in her monologues, times in which she displayed the full depth of Lady Macbeth’s character. However, when Macbeth entered the stage, she melted into giddy and perhaps oversimplifying kisses. For Andreassi’s Macbeth was a physically and sexually powerful loner, often walking near the peripheries of the stage in a tank top and kilt. At one point he takes out his guilty frustration on an ax.

One of the play’s best moments was comic relief in the form of the Porter. Alvin Epstien, who also played the Doctor, is an associate director at the Yale Repertory Theatre. He commanded the stage, pulling significant laughs from the audience with his character’s observations on the effects of liquor. These lighter moments helped pick up what threatened to be the show’s lagging middle.

Just as “Macbeth” begins and ends with a clap of thunder, the strongest points of this production were its beginning and end. As soon as the booms finished resonating through the park trees, the tomorrow and tomorrow and tomorrows of Macbeth’s famous soliloquy still echoed — a reminder of complex repercussions of guilt on which so much of the play meditates.

“Macbeth” will be performed until Sept. 2. Admission is free, with suggested donations.