Complex sentence: He kidnaps Granville, imprisoning him within his own house, and disguises himself to take Granville's place, as the frail old man in a clean room, necessary for his health, with the only other person allowed past the glass barrier being his doctor.
Split into simpler sentences: He kidnaps Granville, imprisoning him within his own house, and disguises himself to take Granville's place, as the frail old man in a clean room, necessary for his health. The only other person allowed past the glass barrier being his doctor.