Wht i think is Mahesh could secretly send kajri to patil house as his agent by letting her marry dev since mahesh knows how fascinated dev ws by seeing her n now dev will also want a revenge which he may think he can get aftr marriage. All something lk dhoom movie n eventually later kajri seriously in lov wid dev n trying to turn his bad things into gud bt now breaking her deal wid mahesh fr her husband's love.