The closer the Doctor comes toward gaining the Governor's confidence, the closer Sil's coup with the Chief Officer and the Mentors' extortion of Varos comes to light. Sil's anxious for the Doctor's silence, and to that end the Doctor and Jondar are promptly escorted to the gallows while Peri and Areta are whisked away to Quillam's research center, where a tissue transmogrifier awaits to permanently change them into animals.
—statmanjeff