The monotony of a pea-soup fog shrouded London is broken by a sudden visit from Holmes’ brother Mycroft. He has come about some missing secret submarine plans.
Seven of the ten stolen pages were found with Arthur Cadogan West’s body. He was a young clerk in a government office at Woolwich Arsenal whose body was found next to the Underground tracks near Aldgate, his head crushed. He had little money with him (although there appears to have been no robbery), theatre tickets, and curiously, no Underground ticket. The three missing pages by themselves could enable one of Britain’s enemies to build a Bruce-Partington submarine. How did he get there and where are the missing documents?