If any movie of the '80s seemed ripe for a sequel, it was this enormously popular time-travel fantasy from the directing-writing partnership of Robert Zemekis and Bob Gale. In fact, BACK TO THE FUTURE's creators were so confident that they shot two sequels back to back. This one picks up where the original story left off. All's well in the new and improved McFly household, where teenager Marty (Michael J. Fox)— barely recovered from his exhilarating sojourn to 1955 — and his sweetheart, Jennifer (Elisabeth Shue), are about to resume a normal life when Doc (Christopher Lloyd) arrives in the DeLorean time machine. Marty and Jennifer are urgently needed in the future, and soon all three are propelled forward to the year 2015, where Marty must prevent a crime involving his teenage son that would bring disgrace to the future McFly family. The permutations of cause and effect have served as a story premise for many a movie, with success generally measured by how neatly events fall into place by journey's end, or whether some moral purpose has been served by the device (as in IT'S A WONDERFUL LIFE). BACK TO THE FUTURE PART II is ever-aware of the need to explain the complications of geometric time and space travel, and attempts to do so chiefly through Lloyd's frenetic ramblings and often-unintelligible discourses. But the film works best through its magnificent technical achievements (the visual effects received an Oscar nomination) and the inherent charm of Fox, Lloyd and, especially, the delightfully menacing Thomas F. Wilson, reprising his role as the awful Biff Tannen. In light of the comically rich performance turned in by this deceptively facile actor, perhaps the alternate title for BACK TO THE FUTURE PART II should have been BIFF'S STORY.