 Riley's brother Seth Costello (Miles Higson) discovered that she and his father had an affair, so she lied about falling pregnant to prevent the truth from coming out.On the advice from her mother Myra McQueen (Nicole Barber-Lane), Mercedes planned to fake a miscarriage, but Mercedes' sister Jacqui discovered the affair and Mercedes' intention to fake a miscarriage.Jacqui was "disgusted" and threatened to expose the affair; Metcalfe commented that this left Mercedes feeling like her "world could collapse around her at any moment".