After all the fears that comic books were filling young minds with notions of deviant sex, it turns out that at least one superhero character really was. Wonder Woman, created by psychologist William Marston, was indeed designed as a vehicle for his theory about the need for dominance and the desire for submission. It also turns out that feminists who decried Wonder Woman as a sex object were at least partly correct: She was inspired not only by Marston’s wife but by the female lover they brought into their marriage.

“Professor Marston and the Wonder Women,” Angela Robinson’s feature about this little-known back story, adds several more delicious complications to the pop-culture icon known as Wonder Woman. Is she an empowered female or just male eye candy? Did she finally level the gender playing in this summer’s hit movie “Wonder Woman,” or was her outfit, as filmmaker James Cameron complained, still too form-fitting? Given that she was born of a three-way relationship full of seesawing power dynamics, no wonder she’s been tough to pin down.

advertisement | advertise on newsday

Luke Evans plays William Moulton Marston, a Harvard psychology professor whose wife, Elizabeth (Rebecca Hall), teaches the same subject at Radcliffe. Into their high-powered intellectual orbit falls Olive Byrne (Bella Heathcote), an eager-to-please young student who wants to help with their research. (Side note: The Marstons helped develop the lie-detector machine.) What develops is not a typical male-female power play, however. Instead, Olive falls for William’s charismatic wife. At any rate, the three not only go to bed together, they eventually co-habitate and raise four children together, two by each woman.

For a movie about transgressive sex, “Professor Marston and the Wonder Women” can be awfully tasteful. Even when an unwitting neighbor catches the trio in a naughty-nurse routine, the whole tableau looks fairly tidy and clean. It’s possible that writer-director Robinson (Showtime’s “The L Word”) wants to emphasize love over sexuality in this relationship to ensure that we see it as legitimate. Still, sex ought to be sexy, especially if we’re going to bring in lassos and corsets.

All told, “Professor Marston and the Wonder Women” is a fascinating look at the creation of a popular superheroine who has always seemed especially complicated. As it turns out, there’s a reason.