The only lead to a poisoned female found in New York is that she had just returned from an authentic Old West-style holiday resort in Arizona. The poison takes about 10 hours to take affect so this means she was actually poisoned in Arizona. But the local sheriff won't help them, as it could damage the towns only attraction. Castle comes up with a plan to go there undercover with Beckett as newly-weds. They soon find, backed up by local Sheriff Conklin and by Esposito and Ryan, that the victim was on the trail of both her ancestry and the lost gold of a 19th century major hold-up. Resort staff provides several suspects.
—KGF Vissers