Plot (Spoiler)

During a party at the Griffin house Mort Goldman accidentally steps into Stewie’s time machine (mistaking it for a bathroom), forcing Brian and Stewie to take a return pad and go after him. They find Mort in a Warsaw, Poland synagogue, thinking he is in heaven since he sees dead family members there. They soon realize the date is September 1, 1939, the day of the Nazi invasion of Poland and the beginning of World War II. The return pad breaks and they decide to go to England, where it will be safe to repair it. In England, Stewie realizes that the return pad is out of uranium fuel and Brian suggests they find some in a nuclear-testing facility in Berlin. At the facility Stewie disguises himself as Hitler; the other two disguise themselves as Nazi officers, and obtain the needed uranium. They then encounter the real Hitler (who orders their execution), but they escape on the return pad back to their own time and arrives back in Stewie’s room 30 seconds before Mort entered the time machine. To keep these events from repeating, Stewie kills the version of Mort who traveled with them.