Business had been good on that Fourth of July weekend. The passengers kept coming, and the money was rolling in. I had flown well into the warm summer evening. Dusk was falling, and we had emptied the last of our fuel into the airplane. The day had been hot and muggy, as the Midwest often can be, with temperatures in the high 90s. The airplane struggled on every takeoff; the density altitude was over 5,000 feet, although the lake was only 600 feet msl. The sun was setting in the west, sending shafts of orange plunging through the towering cumulus clouds just over the horizon. I unloaded my last passengers of the long day, and we hoisted aboard our empty gas cans for the fuel run to the airstrip at Monkey Island Resort.