The instrument rated pilot filed an IFR flight plan and weather briefed for a round trip flight from Provo, Utah, to Rexburg, Idaho, and return. Upon arrival at Rexburg, the pilot's son (who disembarked with a second passenger) requested that his father remain overnight. The pilot responded that the plane would be too hard to start and that he had a class to teach in the morning. After a brief stopover, the aircraft departed Rexburg and there was no evidence that the pilot activated his IFR flight plan for the return leg. A Cessna 310 was on an IFR approach into Rexburg during the time of the accident. Low ceilings and snow were reported at the Rexburg airport and accident site, as well as dark night environmental conditions. The aircraft impacted trees at a point approximately 23 feet above ground in a wings level attitude. It then impacted the ground shedding approximately 8 inches of propeller tip before becoming airborne again, whereupon it impacted power lines and then terrain with its engine ultimately coming to rest 1324 feet beyond the tree impacts.