〃Who was the other man with a key？〃
〃The senior clerk and draughtsman； Mr。 Sidney Johnson。 He is a
man of forty； married； with five children。 He is a silent；
morose man； but he has； on the whole； an excellent record in the
public service。 He is unpopular with his colleagues； but a hard
worker。 According to his own account； corroborated only by the
word of his wife； he was at home the whole of Monday evening
after office hours； and his key has never left the watch…chain
upon which it hangs。〃
〃Tell us about Cadogan West。〃
〃He has been ten years in the service and has done good work。 He
has the reputation of being hot…headed and imperious； but a
straight； honest man。 We have nothing against him。 He was next
Sidney Johnson in the office。 His duties brought him into daily；
personal contact with the plans。 No one else had the handling of
them。〃
〃Who locked up the plans that night？〃
〃Mr。 Sidney Johnson； the senior clerk。〃
〃Well； it is surely perfectly clear who took them away。 They are
actually found upon the person of this junior clerk； Cadogan
West。 That seems final； does it not？〃
〃It does； Sherlock； and yet it leaves so much unexplained。 In
the first place； why did he take them？〃
〃I presume they were of value？〃
〃He could have got several thousands for them very easily。〃
〃Can you suggest any possible motive for taking the papers to
London except to sell them？〃
〃No； I cannot。〃
〃Then we must take that as our working hypothesis。 Young West
took the papers。 Now this could only be done by having a false
key……〃
〃Several false keys。 He had to open