PORT TOWNSEND — Falling in love: Sometimes it makes no sense. Yet the two people step out on that precipice anyway — and leap.

So it happens in “Sea Marks,” the story of Colm, an Irish fisherman at a turning point in his life, and Timothea, a passionate woman who lives in faraway Liverpool. Oh, the timing and the place are not smooth for these two, yet they enchant each other and set out to make a life together. We go along with them first to Colm’s remote island and then to Timothea’s urban flat in Key City Public Theatre’s production, previewing this Thursday and opening for a three-week run Friday.

“Colm is a bit of an innocent. He hasn’t been exposed to much of the world,” said Eric Ray Anderson, the Seattle actor portraying the Irishman. Anderson, himself a descendant of fishermen, has long been a fan of “Sea Marks,” written by novelist-sculptor-actor Gardner McKay. McKay penned this Irish love tale to explore how two people — grownups with differing histories — can be surprised by romance in the middle of lives they thought were pretty well set.

Timothea is driven, ambitious — but not in a hard, cut-throat way, said Crystal Eisele of Port Townsend, who plays the Welsh woman who meets Colm at a wedding on the island where he’s always lived. After she returns to her job at a publishing house in England, Timothea receives a letter from Colm. Then come more letters. They’re filled with emotions conveyed in language that speaks straight from his heart to hers.

“The play is beautiful,” said Eisele.

As Colm and Timothea embark on a torrid affair, they discover how different they are. Colm wonders who he would be if he lived in her city. Timothea seeks to understand her man. In him, she sees a joy and purity that has been rare in her life.

“There is a lot of love underneath it all,” said “Sea Marks” director Allen Fitzpatrick. This play is a friend of his; he directed an Off-Broadway production of it in New York City years ago and has been fond of it since. Fitzpatrick, who has also acted and directed shows in Seattle and around the country, likes the way “Sea Marks” delves into romance between people in middle age. In this production Colm is 54 and Timothea 46; she’s been married and divorced while he’s always been a bachelor.

All this being said, the play has many sweet, comic passages, added Fitzpatrick. Whatever their ages, the pair have moments when they feel like young lovers. It’s that mystical force at play again.

“Sea Marks” curtain times are 7:30 p.m. Thursdays through Saturdays and 2:30 p.m. Sundays this week through Oct. 19. Tickets are $24 to $29, with a pay-what-you-wish performance at 2:30 p.m. this Sunday. The venue is the 66-seat Key City Playhouse, 419 Washington St., which opens an hour before show time.

Ticket purchase is available at 360-385-KCPT (5278) and KeyCityPublicTheatre.org; if a performance is listed as sold out online, patrons are encouraged to come early to the theater to see whether overflow seating is available. Walk-up ticket sales are also possible from 1 p.m. to 3 p.m. Wednesdays through Fridays at the playhouse.

The nonprofit Key City Public Theatre, in its 61st season, receives support for this show from Key City Fish Co. of Port Townsend and from season sponsors Aldrich’s Market, Alchemy Bistro, Edensaw Woods and Avamere at Port Townsend. The 2019 season is dedicated to the memory of the theater’s good friend and longtime patron, Dan Huntingford, former owner of SOS Printing.