Complex sentence: Knowing that Skaldak will desire vengeance for being attacked, the Doctor and the crew chain Skaldak, who sends out a distress call for others of his race to find him.
Split into simpler sentences: Knowing that Skaldak will desire vengeance for being attacked, The Doctor and the crew chain Skaldak. The restrained Skaldak sends out a distress call for others of his race to find him.