Complex sentence: Arriving by ship Tessa, Marta, and their luggage are being transported by carriage and wagon inland to the Alvarado Hacienda when they stop to assist a broken down wagon they are set upon at gunpoint by masked robbers.
Split into simpler sentences: Arriving by ship Tessa, Marta, and their luggage are being transported by carriage and wagon inland to the Alvarado Hacienda. When they stop to assist a broken-down wagon, they are set upon at gunpoint by masked robbers.