Sherlock Holmes and the Circus of Fear (Adventures of Sherlock Holmes)

Why were dreadful accidents happening at Sanger's Circus? Who had poisoned the lion? And why was the trapeze rigged up to kill? Sherlock Holmes's skill and ingenuity is stretched to breaking point as he ponders and investigates. What is the secret behind Sanger's death, and how was his death linked with treasures that belonged to another nation?