Two twelve-year-olds, one short and wiry, the other an overstuffed ragdoll, one all-American from Minneapolis, the second part-everything from Paris, both newly arrived in a small Colorado town--after a shotgun introduction they become immediate friends and begin building a crazy octagonal split-level tree house. Sounds like regular kids' stuff with an assist from complementary characters and contrasting background and it might have been good fun if Mrs. Carlsen had left Monty and broken English Mike to their own devices. But Monty has a rich uncle who dabbles in Oriental mysticism and sends suitable mementoes from time to time; this time it's a tiger head whose eyes burn bright with close-ups of local activity, once an approaching flood, then an attacking dog, finally a little boy lost. All this advance information makes heroes and sometimes fools of the boys but Phineas, the tiger, not content with being a seer, is also a spirit stalking at night with somewhat uncertain intentions. Fortunately (for the conclusion) Uncle Monty recalls him, substituting the skeleton head of a cow... which glows green, beginning the skullduggery all over again. The author virtually abandons the situation she set up initially to convince us that seeing is believing. It's too much to ask, and the story's not worth it.