The seventh escapade for the Frederickson brothers, Mongo and Garth--who now read a needy child's letter to Santa, discover that she's being sexually abused by Reverend Billy, and set out to rescue her. There's no return address on the little girl's letter', but dirt particles within it seem to come from the Amazon rain forest, leading Mongo and Garth to Botanical Garden consultant Dr. Craig Valley--who tried to import Ions of the stuff for mega-millionaire Henry Blaisdel's Nuvironment, Inc. But Valley kills himself rather than talk to them, ditto two Nuvironment goons, and soon Garth is manacled to a bomb in the Nuvironment abandoned office, Mongo is fighting for his life on a New York pier, and McCloskey of the N.Y.P.D. can't make heads or tails of it all. Nonetheless, McCloskey saves both brothers and helps them commandeer an SST to fly to Boise in a blizzard, where the Nuvironment nuts have built a biosphere to protect them when Armageddon arrives (on New Year's Day, when their bombs blast the major world cities to smithereens). The brothers breach the biosphere, rescue little Vicky Brown, dismantle the bomb mechanisms, and get to celebrate Christmas at home with Vicky as their guest. Toned-down, less hyperbolic Chesbro--but, still, a highly improbable p.i. caper, with gratuitous sadism and cartoon heroics.