
Puzzle setter John ‘Ludwig’ Taylor’s life is upended when his identical twin, DCI James Taylor, disappears. John reluctantly assumes his identity in order to track him down.

On a mission to crack the code in his twin’s notebook, John returns to the police station. A frustrated Lucy takes matters into her own hands and plays detective herself.

A new case takes Ludwig on a walking tour of Cambridge, where he’s faced with an impossible question. Meanwhile, Lucy goes undercover and makes a grim discovery of her own.

A body falls from the fourth storey of a construction site. Was it just a terrible accident, or a perfectly executed murder? When things don’t add up, John questions his abilities.