Complex sentence: Back home at Marlinspike Hall, Haddock hires Clodion as his cook, and Calculus keeps Romulus as a pet and a test subject for his inventions of a flying birdcage.
Split into simpler sentences: Back home at Marlinspike Hall, Haddock hires Clodion as his cook. And Calculus keeps Romulus as a pet and a test subject for his inventions of a flying birdcage.