'The Mysterious Cylinders'

5th adventure in the collection Sant of the Secret Service.
An explosion in a public garden in London has the authorities in deep concern because found there were several small cylinders filled with the explosive thought to have caused such destruction in the bombing. The explosive material was new and obviously powerful. Who made it? What was it made of? What was the overall objective? Gerry Sant's planned vacation with his fiancée is put on hold.
It is told in four chapters entitled:
The Mysterious Cylinders
Spy's Letter Deciphered
A Message from the Herrengasse
The Admiral's Secret