A bloodhound named Nick Carter followed a trail that was 300 hours old in 1900, and in Oregon in 1954 another hound worked a 330-hour-old trail to find a missing family. This episode explains how a dog that looks like a sleepy cartoon outperforms any sensor. Nearly 300 million scent receptors do the processing, long ears sweep shed skin cells up from the ground, and the loose wrinkled skin known as the shawl holds those particles around the nose.

None of it is natural. The breed traces to the Saint-Hubert monastery in Belgium around AD 1000, where monks bred slow, silent hounds to work cold scent on a leash. King Charles IX mocked them as fit only for people with gout, yet in Britain they became sleuth hounds set on outlaws and border reivers. The episode also takes apart the polite claim that the name means a dog of noble blood, and counts the health cost of centuries of extreme breeding.

• Humans shed about 40,000 skin cells every minute, and the gases released as bacteria feed on those skin rafts are what a hound follows.
• The noble blood story was promoted by a 19th century French breeder selling to Victorian society. The name first appears in the 1330s and originally meant a hound that followed the blood of wounded game.
• Bloodhounds trail rather than track, following the drifting scent plume and cutting corners, and are trained to plant their paws on the chest of the person they find.
• A 2024 UK study put average lifespan at 9.3 years against 12.7 for purebred dogs, with bloat blamed for 34 percent of deaths in one survey and cancer for 27 percent.
• Knotty, Best in Show at Westminster in 2005, died in 2008 of a rattlesnake bite taken while placing himself between the snake and his owner.