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Our best agent is tracking down a murder/blackmail case. He was periodically checking in with us, but we suddenly lost contact. Here is his last transmission:

F6AC3CF7C2CE1BE2CD3CF5FE1F2CD4AC3B2CD3F8CA2CD3BE9CD2B5

I cannot decode it. It's clearly a hexadecimal string, but what do I know ... please help!

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The message is ...

... only superficially a hexadecimal string. The string follows a pattern: One or two letters are followed by a single digit. The letter combinations that occur in the message are:

B, C, F, AC, BE, CA, CD, CE, CF, FE

You can reformat this ...

... by lowercasing the second letter and you see that these are symbols of chemical elements, namely:

B Boron (5)
C Carbon (6)
F Fluorine (9)
Ac Actinium (89)
Be Beryllium (4)
Ca Calcium (20)
Cd Cadmium (48)
Ce Cerium (58)
Cf Californium (98)
Fe Iron (26)

Usually, in such cases ...

... the atomic number is used, but here the number after each symbol just specifies the letter to take from the element's name. The message begins with

F6 Ac3 Cf7

which decodes to the 6th letter of FluorIne, the 3rd letter of AcTinium, the 7th letter of CalifoRnium and so on.

The message reads:

I traced film to dead man.

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  • $\begingroup$ Well done. And I thought this one would be hard. $\endgroup$ – Paul Beckingham Jun 5 '16 at 19:33
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    $\begingroup$ Thanks. Oh, it wasn't easy without anything to go by except the message itself and I was about to give up. But when I saw the pattern, it clicked. I was probably just in the right frame of mind, because I've used that pattern in another answer recently. $\endgroup$ – M Oehm Jun 5 '16 at 19:41
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    $\begingroup$ Theree are two hints in there, which I think I'll reduce to zero next time. $\endgroup$ – Paul Beckingham Jun 5 '16 at 19:46
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    $\begingroup$ @PaulBeckingham I would recommend leaving the second sentence unchanged. People are generally not fond of puzzles where there is a string of characters without any indication of how to decipher them. This one gives just enough guidance as it is. $\endgroup$ – Gordon K Jun 5 '16 at 21:11
  • $\begingroup$ @GordonK Thanks, I agree with you. There needs to be something to chew on. $\endgroup$ – Paul Beckingham Jun 6 '16 at 3:00

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