Ahoy, Hallow’s Eve Mateys!

He only looks like Ian Alderman, an ordinary harmless Westvillian. And that U‑shaped space dark and dank down by the West River? It only appears to be the tunnel under Edgewood Avenue.

Shiver me timbers, don’t be fooled. Come Halloween, Alderman will have become Captain Thunderbolt, a late 18th century local pirate who terrorized the neighborhood. The tunnel will have been transformed into a spectacular skull-and-bones festooned vessel.

A Broken Umbrella Theatre is hoping to start a new New Haven tradition by mounting a one-day free Halloween theatrical extravaganza and community event come this All Hallows Eve, Oct. 31.

The shows, 40 minutes of harum scarum fun under the tunnel, will be presented on continuing basis, from 2 to 6 p.m.

“We realized there was something missing in New Haven in terms of Halloween, a genuine communal event that celebrates local lore in a unique way,” said Rachel Shapiro Alderman.

She will play the role of the farmer’s daughter who is her husband’s — that is, Thunderbolt’s — object of obsessive desire. She is one of a crew and cast of 20, including Ryan Gardner, who plays one of the nine pirates as well as being the master of the spectacle.

One recent day they checked out their locale and pointed toward the pathway to Coogan’s Pavilion on the Whalley Avenue side of the park.

That will be the starting-off point for the event for those who like to combine a relaxing hayride with being scared to death. Family friendly 10-minute hay rides, gathering at the pavilion, will transport the audience to the spooky tunnel. (You can also park on Edgewood and walk down.)

When they arrive, visitors will see a pirate vessel, curtained and divided into four lantern-lit venues, with the dramaturgy capitalizing on the handy West River. From those waters, evil Thunderbolt and his maritime cutthroats will arrive.

A Broken Umbrella’s previous work has ranged from Waiting for Godot to productions for children in connection with Westville’s Art Walk.

With Thunderbolt — the fellow was real enough to have been punched out by Aaron Burr in a bar brawl at Fountain and Whalley — Rachel Alderman said the company will mount far more than a Halloween play. The aim extends to filling a general theatrical void in town, she said— tapping dramatically into the glory of the city’s parks, public spaces, and local history.

Guitar and cello music composed by Robert Shapiro will accompany the melodramatic mayhem. The event also features pumpkin cut-out activities for little kids (under age 8 are not recommended to attend the play) and The Cupcake Truck for all.

The play, with research by local historian Colin Caplan, written by Kenneth Baldino and directed by Ian Alderman, is being presented in partnership with the Friends of Edgewood Park, the Westville Renaissance Alliance, and the parks department. Hayrides begin at 2, with the last show at 6. For more information, call Rachel Shapiro Alderman at 823‑7988

“We hope to give New Haven something to look forward to every Halloween,” she said.