Sherlock Episode 2.02 The Hounds of Baskerville

Horrific images of a body under attack by a snarling, indistinguishable beast flash in the night as a small boy crashes through a black and haunting moor. He emerges into daylight, terrified, where a woman, out walking her dog, offers help.

Meanwhile, Sherlock needs a new case to ward off his nicotine cravings and feed his hyper-intelligence, and it's that very boy, now a grown man, who arrives in desperate need of help and provides Sherlock's case. As a child, Henry Knight witnessed his father's mauling by a "gigantic hound" in the Devil's Hollow area of Dartmoor. His father's body was never found but the hound became local legend, fodder for both tourists and conspiracy theorists who suspect nearby Baskerville, a top-secret military research complex specializing in chemical and biological weapons and, it's speculated, the weaponized genetic mutation of animals. Knight's therapist had encouraged a healing return to the scene of his childhood trauma. But the experience backfired: standing at the very spot, Knight found beneath his feet the footprints of a gigantic hound.

The hunt is on as Sherlock and John penetrate the high-security labs of Baskerville in search of a demonic hound that may be no more than a delusion. Somehow, in Baskerville's secret basement labs of caged animals and among the ancient piles of stones scattering the moor, science and the supernatural must intersect. But what powers do observation and deduction have in the face of a hellish hound?