Complex sentence: Jericho trails Puck to Scotland and catches up with him just as he is about to be taken on board a U-boat, but Wigram and the police have been trailing them both and the U-boat is bombed and sunk.
Split into simpler sentences: Jericho trails Puck to Scotland and catches up with him just as he is about to be taken on board a U-boat. But Wigram and the police have been trailing them both and the U-boat is bombed and sunk.