SOUTEN - THE OTHER WOMAN tells the story of Mitali [Mahima Chaudhary], married to Ranbir [Gulshan Grover], who belongs to a royal family. While Ranbir is busy expanding his business empire and in the free time indulges in shikaars, Mitali leads a humdrum life. She's bored and neglected.

Enter Raj [Vikram Singh], the kid-brother of Rajbir's business associate Sumer [Shakti Kapoor]. Mitali is entrusted the responsibility of taking Raj around and in a matter of a few meetings, the couple get into physical proximity. The relationship rests on lust and continues to escalate as days progress.

Smita [Padmini Kolhapure], Sumer's wife and Raj's sister-in-law, gets an inkling of the affair and confronts Mitali. But a headstrong Mitali snaps at her and continues to see Raj. Later, Smita makes Raj realize that he has embarked on a path that could've serious repercussions. Raj realizes his folly and makes Mitali understand that it's over between them.

At this point, Rajbir's daughter Sapna [Kiran Rathod] enters the scene. At first, Raj and Sapna have the usual tiffs, but gradually fall in love when they visit Goa for a holiday. When Sapna returns and confides in Mitali that Raj and she are in love, Mitali is shocked, but determined that she wouldn't let Sapna's love story have a happy end.

Immediately thereafter, Mitali spills the beans about her relationship with Raj to Sapna, who is crestfallen to know the truth. Sapna walks out of Raj and heads for Goa again, hoping to make a career in fashion designing. But Raj lands up there and after much persuasion, Sapna relents and forgives him. Mitali also lands up in Goa, this time with a prospective groom in tow for Sapna. A helpless Sapna cows down to her parents' demands and is engaged to the person.

At this juncture, Smita confronts Mitali and tells her to stop playing evil. There's an awakening and Mitali decides to get the lovers married. Simultaneously, Rajbir gets to know of the illicit relationship between Raj and Mitali and is seething with fury.