Dead Ringer (1964)

After 18 years of estrangement, twin sisters Edith 'Edie' Phillips and Margaret 'Maggie' DeLorca are reunited at the funeral of Maggie's husband, Francesco "Frank" DeLorca, who died of cardiac arrest. The rupture in the sisters' relationship: callous Maggie had stolen wealthy Frank from his girlfriend Edie, and tricked him into marriage. As Mrs. Francesco DeLorca, Maggie went on to live a life of luxury; Edie currently owns a seedy bar and is three months behind on the rent. To gain what she believes is rightfully hers after she finds out how Maggie had gotten Frank to marry her, Edie decides to murder Maggie and assume her identity, passing off the dead body as herself, a suicide. Edie must convince Maggie's servants, acquaintances, and friends that she really is Maggie. The most difficult to convince could be golf pro Tony Collins, who had a special relationship with Maggie, of which Edie was unaware. Edie might also have difficulty convincing Sgt. Jim Hobbson, who is investigating Edie's death--and is also Edie's boyfriend. Edie's pose as Maggie is compounded when she discovers the circumstances of Frank's death.