John Stamos’ new true-crime podcast “The Grand Scheme: Snatching Sinatra,” which digs into the 1963 kidnapping of Frank Sinatra Jr., was sparked by a conversation he had on tour a quarter-century ago. “I knew [the rock duo] Jan and Dean from the Beach Boys,” John tells Access Hollywood legal expert Alison Triessl. “Turns out that Dean Torrance of Jan and Dean was best friends with Barry Keenan, who kidnapped Frank Sinatra Jr., and Dean loaned him the seed money to buy a gun and this kind of stuff.” Now, 25 years after Dean pitched him on the idea at a concert, John interviews Keenan about his crime in the podcast. The “Full House” star tells Alison some of the surprising details of the case. Plus, when reflecting on a potential future true-crime podcast, he said, “The problem is I’ll never be this close to another criminal, I don’t think,” adding as a joke, “Saget! Saget. He’s right on the verge of something.” “The Grand Scheme: Snatching Sinatra” is streaming now.