NYC financial advisor, Brandon Bourne and his socialite wife, Jessie, have a seemingly happy marriage of several years. However, about 2 years earlier, Brandon had an affair w/ a younger woman, Isabel Lorrison, who’s now back in town hoping to rekindle the romance. Through a young model/new friend, Rosa Senta (Cyd Charisse- in a rare non-dancing role), Jessie meets Mark Dwyer (a cop-turned-writer just arrived from Italy).
Isabel: It’s all right Brand. What difference does it make? Today or another day? There’s no hurry. You’ll be back.
[Brand turns around and slaps Isabel. Isabel smiles]
Isabel: That’s better, isn’t it Brand! That’s what you don’t get at home. That’s what you’ve missed isn’t it! It’s so tiresome being restrained and soft-spoken and gentlemanly. What you really want is to be a little rotten, like me!
This is a well-made film w/ plenty of clever/memorable dialogue; the pacing is a bit slow at times. I would’ve liked to see more of the West Side (West Village) and more outdoor shots. As several viewers commented, Mason is cool/controlled; he has great chemistry w/ Gardner (and they both have fabulous cheekbones). True, Mason and Stanwyck look like a good couple, but there isn’t much heat. I enjoyed seeing Stanwyck w/ Heflin; his character is very caring, energetic, and charming. They acted together in two other films. There are some gorgeous outfits in this film; the strapless/black cocktail dress that Gardner wears in her first scene is stunning!
Brandon: [Desparately] Jess, can’t you understand what this is for me. I’m like a drunk who knows liquor will wreck him. He hates it. He hides from it. He… he tries!
Jessie: What are you asking for? Permission?
Future First Lady Nancy Reagan (credited w/ her maiden name- Davis) plays one of Jessie’s friends, Helen Lee. Greer Garson, Fred MacMurray and Claudette Colbert were considered for the leads. Gale Sondergaard, who plays Stanwyck’s mother in this film, was only 50 y.o. when this film was made; Stanwyck was 42 y.o. Sondergaard was blacklisted for refusing to testify before HUAC, so didn’t work for the next 20 yrs. Beverly Michaels (platinum “Amazon” Felice Backett) is the wife of Academy Award winning screenplay writer Russell Rouse and the mother of Academy Award winning film editor Christopher Rouse.
 One bit of casting that is interesting is Charisse, as she bore a resemblance to Gardner, so the initial attraction Mason has for Rosa bears out his obsession with Isabel.
Gardner provides all the excitement in “East Side, West Side”…absolutely gorgeous and just about burns a hole in the film with her steamy performance.
 Stanwyck and Heflin have a palpable chemistry here, and Ava Gardner is a most alluring vixen. Cyd Charisse is a delectable ingenue (and a tall drink of water)…
Stanwyck’s scene with Gardner is a standout — both actresses are well matched; Gardner’s feline beauty and laissez-faire romantic approach nicely complements Stanwyck’s humane fatalism — and Stanwyck and Van Heflin are an appealing couple.
 Screenwriter Isobel Lennart was usually good for some smart dialog, and she’s reliably industrious here, though there’s no truth at the center of these doings: People just don’t fall in and out of love as quickly as they do here, and the plotting takes some very improbable turns… Believable it’s not, but it’s very entertaining…
-Excerpts from IMDB reviews