Complex sentence: The plan is temporarily foiled by the arrival of Bitzer, who hopes to obtain promotion from Bounderby by bringing Tom to justice; but Sleary arranges an ambush and Tom is taken to Liverpool where he boards ship.
Split into simpler sentences: The plan is temporarily foiled by the arrival of Bitzer, who hopes to obtain promotion from Bounderby by bringing Tom to justice. However Sleary arranges an ambush and Tom is taken to Liverpool where he boards ship.