The Phantom has introduced a new mode of mail transport for the last leg of the long journey to the Deep Woods: chimpanzees carrying post bags across the inhospitable Great Swamp. The system is soon put to the test, however, as two cornered diamond thieves hide their loot in a monkey mail bag.

The thieves get a lucky break when they learn that Diana is due in Bengali shortly for the Jungle Olympics (see D078 The Gurk Twins) and kidnap her to make a straight swap for the diamonds bag. But the Phantom must tread carefully: the thieves leave a trail of murder and mayhem in their wake...