Complex sentence: Jessie and Roy escape with the train because Roy, a railway enthusiast, knows how to operate a locomotive, but the train starts to slow down and Grinko and Kolzak are able to re-board the train.
Split into simpler sentences: Jessie and Roy escape with the train because Roy, a railway enthusiast, knows how to operate a locomotive. The train starts to slow down and Grinko and Kolzak are able to re-board the train.