Cadogan West's head has been crushed, but it looks like there has been no robbery - was the assailant after the plans? On further investigation, with no evident signs of a struggle or violence inside any of the railway coaches or track-side, our heroes realise that this is definitely no straight-forward mugging. It is clear that the young man planned to sell the plans for profit, but how was he killed, and why, exactly?
Lucky that Holmes, Watson, Mycroft and friends are on the case - rest assured they'll find their reason - and their man.
Edward Hardwicke is a remarkable narrator: he does so many different parts and soon you feel that you're listening to four or five different people.