The LaFontanne Chemical Company is shipping out a load of we're not sure what, disguised as something entirely different. Mr. Pereaux and Mr. Grock don't want that shipment to ever arrive anywhere, and they and a man named Aquirre mean to stop it at any cost. The ship's owner, Mr. Fontanne, smells a large rat and calls Chan in on the case, since the famous detective is in New Orleans because, well, because he felt like being in New Orleans, I guess. Chan gets what facts there are from LaFontanne, who is promply set upon by a gang who attempt to kidnap him, but fail. Mr. LaFontanne's partners come up with some insurance; just by chance they tell him, a partnership agreement (why they would have been running a company all this time without one is another large mystery which will not be solved) that bestows upon the living partners the portion owned by a deceased partner. Then the guy who invented the formula for the poison gas that the company is making but who was, in his opinion, swindled out of his rights to make a profit from it, shows up and threatens LaFontanne with a gun. Well, he turns out to be a harmless crank. Or is he? Everyone seems suspect, clues are boundless but don't seem to fit into any particular pattern or too many patterns, take your pick. But Chan must solve the mystery before Monogram is depleted of out-of-date film stock. Can he?