Complex sentence: The night of the delivery, North Wind's minions attach heating and cooling units to the bottom of the sleigh, apparently capable of heating or cooling entire regions of the planet, making the Brothers think they both double-crossed each other.
Split into simpler sentences: The night of the delivery, North Wind's minions attach heating and cooling units to the bottom of the sleigh, apparently capable of heating or cooling entire regions of the planet. Their discovery causes the Brothers think they both double-crossed each other.