Inspector Jane Watson, of New Scotland Yard, paid a call on her good friends Dr. Shirley Holmes, and her roomie, the famous consulting detective Georgia Lestrade. Ms. Holmes answered the door.

"Good day, Jane, and what brings you here today?"

"Good day, Shirley; I'm afraid I need to consult with Georgia. We've been on the trail of a gang of bank robbers, and we've reached a bit of an impasse - we know that the robbery is going to happen to-morrow, but we still have no clue on the target or time."

"Do come in; she will be back momentarily. May I offer you tea? Or perhaps something a touch stronger?"

"I think not, but I would ask you for simple water."

As Holmes handed Watson the requested water, Lestrade walked in. "Jane! So good of you to visit! But I see that you've come in a more-or-less official capacity. So what is it that troubles New Scotland Yard?"

"Well, Georgia, as I told Shirley, we're on the track of a bank robbery about to 'go down'. But we still don't know where or exactly when, just that it's to-morrow. We did intercept an email message between two of the gang; perhaps you can decipher it?"

OSCAR IS WAVING. 15152 33604 27000 20117 14451 21414 46241 60000

Lestrade stared at it for a minute, and reached for her iPad. "Just a moment..." She tapped on the tablet briefly. "Ah yes, this answers the question nicely. You'd do well to deploy your team to..."

Where, and when, is the robbery going to happen?



This is a clue for us to use flag semaphore (a system of communication involving two flags - at sea, the flag for O (Oscar in NATO phonetic) is used). Therefore:

15152 33604 27000 20117 14451 21414 46241 60000

Break these up into pairs of numbers. Label the hands at 0 referring to the bottom position (as typically resting position places both hands there). Then, label the other positions 1-7 going clockwise (which would make 01 = A, 02 = B, ... 07 = G) Then, we may use a flag semaphore table to convert letters. Hence, we get: LLOYDS BANK[signal numbers]HKKJPM. That last part makes no sense until you read how numbers are signaled, setting a "flag" setting (no pun intended) up and down. So the last bit actually reads: LLOYDS BANK[signal numbers]800[signal letters]PM, or parsed better LLOYD'S BANK, 8:00 PM.

  • $\begingroup$ On the nose! I'm a bit curious as to how you managed to decipher the initial clue so quickly. And how you worked out the conversion between that system and the numbers. $\endgroup$ – Jeff Zeitlin Feb 11 at 12:43
  • $\begingroup$ Based on the fact that all of the numbers were 0-7 (plus pairs of numbers were always internally sorted and never the same save for 00), flag semaphore seemed likely. I deduced the position of 0 by considering the resting position of the flags, and it seemed likely that the other numbers would be naturally assigned either clockwise or counterclockwise. $\endgroup$ – phenomist Feb 11 at 20:04

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