Part I: Marty struggling to get the DeLorean started after it stalls on him, whilst 1955 Doc tries to reattach the cable to the top of the clock tower before the lightning bolt strikes at 10:04 PM.
Part II: Marty uses his hoverboard to try to retrieve the Sports Almanac from Biff in his car, as the struggle continues into the tunnel.
Part III: Doc and Marty attempt to push the DeLorean up to 88 mph with the locomotive before falling into the ravine, while Clara boards in an attempt to get Doc to notice her again.