I didn’t get the butterfly reference, but it seemed like a similar plot device to the truly AWFUL movie Signs — where the little girl inexplicably leaves full glasses of water all over the house, and people keep buying new cups instead of putting them away — and Johnny Cash swings the baseball bat, as instructed by a dead woman given clairvoyance after being pinned to a car. And Gibson knows to tell him to “swing away”, because water kills the aliens who mastered space flight and invaded earth and are all knowing but would clearly all die if IT FUC*ING RAINED.