The accident airplane collided with terrain during initial climb from a private landing strip. The intended destination was the annual EAA fly-in at Oshkosh, Wisconsin. Night VMC conditions prevailed. An aural witness heard what he described as a 'regular airplane engine.' He stated it started racing and going real fast and then he heard 'little pops.' He saw the sky turn orange. Shortly after that the town fire alarm sounded. The pilot of the accident airplane was a dentist and worked all the previous day. He then flew a four hour flight and returned to the departure airport about 2230. The accident flight occurred about 0310 the following morning. The runway used was 1700 feet long and 45 feet wide. A mature tree line crossed the extended centerline approximately 700 feet south of the runway. The airplane impacted about 360 feet southeast of the departure end of the runway. The flight path was over unlighted farmland and the moon was below the horizon. No mechanical defects were discovered in the airplane or powerplant.