His wife had considerable wealth that she set aside for their daughters when they married.
Roylott had a violent temper and beat to death a butler whom he suspected of theft.
He knew the snake's poison would be untraceable, so he wouldn't be suspected of murder.
When Holmes attacked the snake on the bell pull, it went back through the ventilator and bit Roylott instead.
A Victorian bell pull, or a vertical rope attached to a bell, was used to summon servants; a ventilator is a vent.
The ventilator connects with Roylott's bedroom, and the bed is bolted to the floor so it can't be moved away from the vent.He liked Indian animals, and bought a baboon and a cheetah to live on his property. As the wedding date approached, she began hearing a strange low whistle at a.m.One night, Helen heard Julia screaming in her bedroom, then a low whistle and a metallic clang.Helen began to hear the whistle her sister mentioned just before her death. Holmes arranges to visit Helen at the estate with Watson the same day while Roylott is out.After she leaves, Roylott (who has followed her) bursts in and threatens them if they investigate. During their investigation of the house, Holmes finds a dummy (non-functional) bell pull and ventilator in Helen's room.Roylott brought his daughters to his family estate at Stoke Moran.He forced them into a reclusive life and attacked the locals.After a long prison sentence, Roylott brought his family to London.Soon after, his wife was killed in a railway accident.In the end, he's much like the swamp adder - deadly when provoked.In ''The Adventure of the Speckled Band,'' Helen Stoner asks Holmes for help when she feels threatened living with her stepfather, Dr. Roylott had a medical practice in India, where he met his wife, and the couple had twin daughters, Helen and Julia.