Niamh is present as a patient, Anthony, falls from a great height and dies, as his twin brother William watches on. Rob is tasked with finding out what happened to Anthony and has to dig deep to uncover the truth about what happened.
Rob questions Antony who tells him that he spoke to William in his office and his resentment got the better of him when he saw his brother so happy. He snapped and attacked William with a paperweight.
The only way he could get away with it was to switch identities with his brother and make it seem like suicide. He could have made a getaway before anyone realised, but he ran into Niamh in the hall who immediately realised the switch. Rob charges Anthony with murder.