Joan researches tech billionaire Oden Reichenbach, who made a huge donation to a gun-buyback program she had started. He wants to meet her. A female runner drops dead short of the finish line with a knife in her back. Sherlock pinpoints the likely crime scene in the park where the race was run. He and Marcus find a moonshiner's shack. The runner was likely a witness to a murder that took place there. Oden takes time out from archery practice to meet with Joan. Oden wants to hire Joan and Sherlock to protect his niece Abigail, who someone within his company is threatening to kidnap. Dredging a pond near the shack yielded bodies of the moonshiner and a hog. The hog was killed with risin. Sherlock finds a fingerprint on an antique wine bottle at the shack. Sherlock locates a suspect at Oden's company who may have a gambling problem. The fingerprint Sherlock found leads to a shot wine dealer, who was the first victim. He tells Marcus an intruder was looking for a particular vintage of wine. The killer plans to inject risin into those wine bottles. The target is a hedge-fund magnate, Jason Wood. Sherlock's suspect in Oden's case doesn't pan out, as he was profitting from a private poker room instead. They hope to draw out the killer by having the Woods attend a wine auction that night. The surveillance feed cuts out. Two poisoned bottles are slipped in. Marcus seals the room, then has to let people leave. They catch the killer, Colby the bartender Marcus had earlier interrogated, who was obsessed with Jason's wife. Oden invented the threat to Abigail as a test of Sherlock and Joan. He was working with Patrick Mears as part of a vigilante force, and he wants to recruit them.