Death Collector by Justin Richards

In Victorian London, Albert Wilkes returns home for tea four days after his funeral. While his shocked and terrified wife rushes to prepare it, Wilkes takes the family dog for a walk and is abducted. His kidnapping is witnessed by young pickpocket Eddie, who becomes embroiled, along with an assistant at the British Museum and a clergyman's daughter, in a deadly plot involving the fragments of a diary, a secret department at the British Museum, and a dinosaurlike creature roaming the streets.