L'Engle's irksomely superior Murry family reassembles here for Thanksgiving dinner, about ten years after Meg and Charles Wallace braved the Wrinkle in Time to rescue their scientist father from malevolent cosmic forces. Now Mother has her Nobel prize; the mundane twins are in law and med schools, respectively; Meg is married to old friend Calvin O'Keefe and happily pregnant (but more bland and vacuous than she ever was before); Father is a confidant of the President, who calls him now simply to unload his worry about the imminent nuclear war threats of South American dictator Mad Dog Branzillo; and precocious Charles Wallace, now 15, leaves his tesseract model and goes off to his star-watching rock to see what he can do to avert disaster. There, with the wind making the decisions and the evil echthroi trying to catch him en route, Charles rides a unicorn back in time and goes "Within" a series of individual consciousnesses. Through these psychic stopovers L'Engle tells of two Welsh brothers who came here before Columbus and fought over an Indian maid, and of their descendants from Puritan times straight on down to Mrs. O'Keefe--now Meg's bitter, inarticulate mother-in-law, who has roused herself just long enough to provide Charles with a rune and charge him with the mission. The idea, according to the unicorn, is for Charles to influence a Might-Have-Been which determines whether Branzillo is descended from the good or the bad line, and thus (?!) whether he will or will not start a nuclear war--a shaky if not asinine premise on which to build an earth-tilting adventure. The Madoc-Maddok-Maddox-Mad Dog family saga grows in interest as Charles gradually figures out all the connections, but--though his mission succeeds somewhere in the 19th century--we never see him as anything but a passive, if uniquely present, onlooker. Meg's role is even more passive and less engaging, as she alternates between wringing her hands in the family kitchen and stroking a strange dog on her attic bed while fretfully following Charles Wallace's adventures in her "kything" mind.