Inthisstory,a4-year-oldbabynamedBobbyaccidentallytransformshisbodyintothatofa30-year-oldmanusinghisgrandfather'sgenetictransformationmachine.Bobby'ssiblings,realizingthetroublethey'reiniftheirparentsfindout,trytocatchhimbeforetheirparentsreturnfromvacation.Meanwhile,therearealsobadguyswhowanttogettheirhandsonthevaluablemachine.ThesiblingshaveonlyonedaytochangeBobbybackbeforethemachinelosesitscapabilities.It'saraceagainsttimeastheynavigatethroughvariousobstaclesandadventurestosaveBabyBobbyandrestorehimtohisoriginalform.