Complex sentence: Outside, they spot Victor Foxtrot, its crew and passengers under the assumption they are at Heathrow, performing slave labor under the control of Plasmatons, humanoid blobs of protein held together by the psychokinetic field.
Split into simpler sentences: Outside, they spot Victor Foxtrot, its crew and passengers under the assumption they are at Heathrow. However, they are performing slave labor under the control of Plasmatons, humanoid blobs of protein held together by the psychokinetic field.