Jennifer Bareilles, Michael Medici PHOTO BY SUSAN RAGAN

This is the story of the eternal triangle: a philandering husband named Michael, a corrupted twat named Abby and a condemned wife named Linda. Before the play is over, Linda must die. Fiction by Steven Dietz is an exploration of relationships under stress. Now playing at the Phoenix Theatre, this intensely realized production takes the audience directly and succinctly into the life of a married couple, along with his dalliance, her disease and their literary aspirations. The show uses a simple, straightforward set design and well-defined time and place settings.

The story is engrossing, the characters are appealing, but the plot complications are surprising.

Michael Waterman (played by Michael Medici; also the set designer and perfectly competent in his role as a self-absorbed writer) meets Linda, soon to be Mrs. Waterman, at a Paris sidewalk café. They click. They hook up. They are both writers; in their careers they put words together to influence other people. “The lies begin when you lift your pen,” she says. Linda teaches creative writing.

Then she finds the journals of her husband, the charming scoundrel. He had attended a writers’ colony and had an affair with the officious, perfunctory, young, and needy curator of the program Abby (Jennifer Bareilles.) The truth eventually comes out. Linda remarks that Michael has written many journals and only seven do not talk about Abby.

Linda and Abby meet. They attempt to bond. Meanwhile, Linda is dying of cancer. The interactions of this triangle are loving and forgiving. Heated arguments give way to warmth as the three of them learn to accept one another. They discover they had something in common, a sight in South Africa where the Indian Ocean meets the South Atlantic. They both saw a white line in the water at this confluence. Linda’s reaction to it is quite different from what happened to Abby there.

But unanticipated complications arise. The story of Linda’s fatal disease leads to a recollected meeting at their sidewalk café. Abby drops a bombshell on Michael: she only hooked up with him because of her past sexually violent experiences. In the end, only Linda finds comfort in death.

With just the café table, an easy chair and a writing table, director Richard Harder has created, along with well focused lighting by Colin Cross, a sense of distinct, non-overlapping spaces. The set elements, arranged in a triangle, echo the dynamics of the story. He has been able to present Michael as vulnerable and self-effacing, despite his affair. Joyce Henderson as Linda is sympathetic, but not cloying. She spends much of the time calmly observing the affair from her easy chair in the shadows. The actress shows professional concentration and character inhabitation during this hour and thirty-six minute play.

The play is extremely complex while seeming very simple. Many threads of different colors are introduced early on. All of them eventually tie in to a coherent tapestry. All hues blend to a vivid collage by the end. The line leads straight to the theme of the story: unconditional love; acceptance; forgiveness. Each character loses something.

Fiction, a production of the Off Broadway West Theatre Company, continues at the Phoenix Theatre, 414 Mason Street, San Francisco through March 31. Tickets ($30) are available by phone at (800) 828-3006 or at www.offbroadwaywest.org.