The ancient Greeks teach us that tragedy and comedy are two sides of the same coin. Try too hard to create drama and instead of sending shivers down your reader’s spine, you’ll send her into fits of giggles.

I was reminded of this hilariously the other night by the 1951 Bette Davis film, “Another Man’s Poison.” It is a howler, in no small part because of the wind-up plot. Davis’s over-the-top effort to drain every drop of noir out of the bloodless script sends it out of control. Davis, warns TMC’s Robert Osborne, “pulls out all the stops and gives the best impression ever given of Bette Davis.”

So fasten your seatbelts — here’s what happens in a mere 90 minutes. (In italics, in case you don’t want me to spoil it for you.)

Thriller writer Janet Frobisher (Davis) returns to her darkened home after her young lover rebuffs her. She is greeted by George (Gary Merrill), who announces he and her husband robbed a bank and her husband killed a police officer. Janet confesses she has poisoned said husband with medicine meant for her horse and his body is lying in the next room.

Since her husband lived abroad and was a stranger to the neighborhood, George tells Janet he will pose as her spouse. She persuades him to get rid of the body and after he dumps it in a local lake, she taunts George that he should have checked for a pulse: Her husband was merely unconscious and now George is the murderer.

Fast forward through some lovely shots of English scenery and much scenery-chewing. Janet pulls her husband’s gun on George and they struggle. He seizes the weapon and only then notices she’s wearing gloves. Now his fingerprints are on the weapon.

George decides to go for a ride on Fury, Janet’s adored horse. She lets him go, hoping the spirited animal will kill him. George returns, looking fairly battered and carrying the gun. Janet cringes. George announces Fury broke a leg and had to be shot. Shortly afterward, the vet tells Janet that Fury’s only injury was the bullet wound.

It’s a dark and stormy night. At Janet’s urging, George drives out into the lashing rain (don’t ask) in a vehicle with bad brakes. It plunges into the lake. He staggers back to the house looking like a character out of “The Fall of the House of Usher” and lunges for Janet. They trade words. Day breaks. The police haul the car out of the lake and also find a body.

Janet decides it’s time for George to commit suicide and poisons his whiskey flask. She invites him to share a drink from a bottle at the bar; he hesitates, eyes their glasses and goes for the flask. Goodbye, George.

The police arrive and Janet learns they’ve known all along George was an impostor. Janet feigns a faint. And is revived with whiskey from the flask. Lights out.

It’s not exactly “Agamemnon” or “Hamlet,” both of which are pretty improbable if you deconstruct the plots. In the hands of the masters like Aeschylus and Shakespeare,  though, silly plots become great dramas filled with towering emotion that transcend time and place. Gripped by the characters’ plights, we forget we’re watching a play

So what went wrong here?

Since the plot of my work in progress contains some rather dark twists, I’ve been giving that a lot of thought. Here’s the short list I came up with:

No passion:  The main characters seem interested in outwitting each other purely as an intellectual exercise. Anger and fear are absent. Lust is hinted at but quickly dropped, and there’s no chemistry between the stars (odd considering that Davis and Merrill had married recently). The movie poster shows a brutal-looking George about to rip Janet’s dress from her shoulders, but they scarcely lock eyes on the screen.

No engagement: George is a cipher. In Davis’s hands, Janet foreshadows Davis’s crazed character in “What Ever Happened to Baby Jane” more than she draws on complex characters like Julie in “Jezebel” or even Margot Channing in Davis’s previous film, “All About Eve.”  Now there was a mistress of manipulation and drama! You care about what happens to Margot, even though she deserves to come out the loser. On the other hand, it’s hard to imagine Janet attracting a willing dinner guest, much less a loyal following for her best-selling thrillers.

Nobody to root for: About the only characters to care about are the tepid lover (who is a louse) and the proper secretary who loves him — but they get engaged and skedaddle from the script with indecent haste. Maybe poor Fury deserves some interest, but he’s not around much either, and it’s pretty clear from his first scene with Janet that he’s toast.

No shades of gray: The main characters are bad, bad, bad. The supporting characters are bland, bland, bland. All are delineated by mannerisms rather than believable personality traits.

No emotional logic: In first-rate drama, character drives action. These characters are pieces on a chess board and about as lively.

What do you think? Why do some thrillers work while other sink into eye-rolling melodrama? What’s your favorite example of either?

(Next week: Is “Wuthering Heights” an iconic love story?)