We never know when the fever will hit us (someone cue Peggy Lee) -- the fever for Mariscos Playa Hermosa's camarónes culichi, or shrimp in green tomatillo sauce. And once we've got the fever, nothing will do but to make a beeline to this humble little place and snarf up a serving of that tangy ambrosia, which includes melted jack cheese and fat, fresh shrimp, with a side of rice and tortillas. Tomatillos may be our favorite member of the nightshade family. When you buy them fresh, they look like jolly green figs, with a paperlike covering over a mini-tomato that has a sticky skin. Inside they're mushy, full of seeds, with a taste somewhat like a green apple. But turned into a sauce, their flavor intensifies, as does their color, and the result is polish-your-plate-with-tongue good. A lot of Mexican eateries make it, but we're partial to Mariscos Playa Hermosa's because it doesn't try to get all precious with it, as do some spots. Rather, Mariscos' is straightforward and immensely satisfying, curing us of "tomatillo fever." Well, at least for the moment.