When Charles Ashton's wife fell from a balcony to her death it was her best friend Anabelle Logan who took charge of the family and made a home for them; but when it comes to a second marriage it is Connie, the attractive actress, whom Charles marries. For Annabelle, who is in love with Charles, for whom she murdered his first wife, this is the last straw. Fortunately, no-one knows of her crime except her old governess Mrs Walworth, and by submitting to a little blackmail the old lady can be kept quiet. Coldly and deliberately, Annabelle lays plans for the destruction of the second Mrs Ashton - her scapegoat is to be Charles' small son Ricky in whom she fosters a hatred of his stepmother. Ricky has always been fascinated by the combination of the large safe his father has in their sitting room - what could be easier than to lure Connie into the safe and then seal the door, at a time when she herself can establish an alibi with Mrs Walworth? But, unknown to Annabelle, Mrs Walworth is killed in an accident, and she finds the alibi a sudden liability instead of an asset. Connie is found in the safe, in time to save her life; but Annabelle, in trying to escape, finds herself caught in the trap she had laid for her intended victim.