After the ovations and when the lights came back up Friday night, the audience that had watched the night’s premier of “Proof” at the Whidbey Island Center for the Arts left well satisfied.

With just four actors and a single set, this David Auburn play — the story of a young woman’s struggle with losing years of her life caring for a once brilliant but later deranged father — is great entertainment. As theater goes, “Proof” is not experimental, nor is it a training ground for untested actors. Rather, it is a venue in which some of South Whidbey’s best actors can tell a straightforward story about the turning point in one person’s life.

In the lead roles are South Whidbey “A” list actors Deana Duncan and Ken Church. Duncan plays Catherine, a 25-year-old woman who has spent the past five years of her life in Chicago caring for her insane mathematician father, Robert, played by Church. As Catherine, Duncan is a crushed soul, floundering in even the smallest ripples on the surface of life. The audience meets her a few days after her father has died. Having devoted all her attention to him for the past few years, she has no idea what to do with the hours, days, weeks and months of her life.

Duncan plays her character as someone who seems to have once been interested in living and following in her father’s footsteps as a mathematician. One of the most expressive actors to work the WICA stage, she nonetheless plays well as a character intent on walling off the existence around her. She is also able to convey a sense of hope when she begins to open up later in the show, something that brings a growing warmth to a show that intentionally starts a little gray and cold.

Church, who has in recent years played over-the-top characters in shows such as “Glengarry Glen Ross” and “Moon Over Buffalo,” works well within a more subdued role as Catherine’s father. During Robert’s best spells in the play — the few times he appears on stage as either sane or dead — he is an encouraging father to his daughter. During his worst, he is convincingly feverish as a madman trying within the damaged machine of his mind to get back the mathematical genius he once had.

Supporting Duncan and Church are WICA newcomer Kevin Partridge as Robert’s former student, Hal; and Kira Keeny as Catherine’s urbane sister, Claire. Partridge brings a breezy, upbeat feel to the stage in every scene, even when in conflict with Catherine and Claire over his relationship with the family and to the work of the sisters’ father. Keeny, who noted after the opening night show that “Proof” marks the first time she has spoken more than eight lines in a scene at WICA, seems as much the old pro as the rest of the cast though she has only two local credits to her name, “Little Shop of Horrors” and the summer’s “Picasso at the Lapin Agile.” She is the character in the play that the audience loves to hate as she swoops into town on the day of her father’s funeral to change Catherine’s life as she sees fit.

To the credit of the actors and director Shelley Hartle, their are no defects in this show — even opening night looked flawless. It has tight timing, makes great use of a flashback timeline, holds a few surprises, and sends an audience away after two hours feeling satisfied. While “Proof” doesn’t really take any risks — in fact, it shares so many characteristics with the unrelated film “A Beautiful Mind” that it is downright familiar territory for most — it is entertaining, emotional and charming. It is definitely the thing to see on an October evening.