After Dean Jones grabs his suitcase off the bed and goes to leave the apartment, the next shot with Jane Fonda in the bedroom shows her sitting on the bed next to the suitcase Dean Jones just left the room with, before she jumps up to follow him.
Near the beginning of the film, Celia leaves in a cab. Moments later, another one pulls up--driven by the same actor.
Jane Fonda has the fancy necklace in the restaurant when the power goes out but doesn't have it in the next several scenes in the staircase, the taxi and back in her apartment. She tried to give it back in the restaurant but it is on her neck when the power fails.