New York City, 1947. Songbird Betsy Sinclair belts out a ballad as P.I. Joe Flynn downs a drink at the Pennybaker Club. The fedora-wearing detective is looking for a dame named Vera Mulqueen. She’s a striking beauty who just happens to look a lot like Beckett. Betsy Sinclair, by the way, is a dead ringer for Lanie. As for Joe Flynn, he bears a striking resemblance to Castle. As you may have guessed, this flashback to the ‘40s has something to do with a present-day murder.
Stan Banks was shot to death in the now-abandoned Pennybaker Club. Stan’s wife says they’ve been separated for about a year after her hubby became a treasure hunter. He was obsessed with finding something called the Blue Butterfly. Castle finds a 1940s diary amongst Stan’s stuff. It belonged to a private eye named Joe Flynn. Castle can’t resist reading the juicy journal. It could be the key to the case. Plus, it’s really cool.
On June 18, 1947, secretary Florence Kennard (looking a lot like Martha) tells Joe Flynn they have a potential new client. Sally Scofield (that would be Alexis) steps into the office in her t-strapped shoes and country suit. She talked her new husband into honeymooning in the Big Apple so she could track down her sister, Vera Mulqueen. She wants Joe Flynn to find this beautiful doll.
When Joe tracks down Vera at the Pennybaker Club, he learns that she’s ruthless mob man Tom Dempsey’s main dame. Two henchmen (picture Ryan and Esposito) teach Joe a lesson about eyeballing someone else’s lady. Vera quickly learns that the handsome P.I. can take a punch. As for Joe, he can see that Vera looks even more stunning thanks to a blue diamond-studded necklace. In the present, Castle exclaims, “The Blue Butterfly! It’s a necklace! That’s why Stan Banks was killed.” He then asks, “Why am I narrating?” Classic stuff.[break]
Rumors are that the million-dollar Blue Butterfly was hidden somewhere in the Pennybaker Club. The supposedly-cursed necklace made its way into the hands of mob boss Tom Dempsey. Castle says the Blue Butterfly was kept in a secret safe at the club. He also claims that Joe and Vera were in love after having known each other just five days. Yes, people got together a lot faster in the ‘40s. Anyway, Castle says Kate’s heart quickened when she and Joe stole a moment together. Wait, did Castle just say Kate? He claims he said “fate’s heart quickened.” Uh-huh.
Back in the ‘40s, Betsy Sinclair plants a kiss on Joe to fool Dempsey’s thugs into thinking he’s with her. After that, Vera wants to skip town with Joe. They could use the Blue Butterfly to fund their getaway. Vera knows the location of the secret safe where Dempsey keeps the necklace. Beckett finds the safe opened in the present day. Castle believes Stan must have found it, too. But who has the Blue Butterfly now?
The bookie that financed Stan’s treasure hunt for the Blue Butterfly alibis out, but another lead indicates that the gun which killed Stan was used in an unsolved double-homicide in 1947. The victims in that killing were Vera Mulqueen and Joe Flynn. The lovebirds were found dead in an alley in a car that was set on fire. Tom Dempsey was the prime suspect in the case.
A white Mustang was seen at several locations related to Stan’s murder case. The car belongs to Tom Dempsey the Third. The mob man’s grandson claims Stan approached him to do a biography on his grandfather. But this guy’s not the killer. Another suspect, treasure hunter Clyde Belasco, hid behind the bar at the Pennybaker when he found out Stan was close to finding the necklace. He claims to have been knocked unconscious with chloroform shortly after he saw the victim holding the Blue Butterfly.[break]
One of those paying respects at the recent funeral of Betsy Sinclair was Jerry Maddox, the old bartender at the Pennybaker. Jerry sheds some light on the case. Sally Scofield was the daughter of the woman Dempsey dumped when he met Vera. Her distraught mother later killed herself. Jerry says that Sally took great joy in the fact that Dempsey died of a heart attack four months after the mob man killed Joe and Vera.
Castle learns that Stan purchased Joe’s diary from the granddaughter of his old secretary, Ruth Hunsacker. He also learns of Joe and Vera’s plan to skip away while Dempsey and his men are busy listening to a big prizefight. He also discovers that Vera didn’t have a sister. That means Sally Scofield set up the P.I. It’s a classic film noir twist. Castle loves it!
Remember how Joe described Sally as a girl who wore t-strapped shoes? Well, Beckett notices a t-strapped shoe in the old crime scene photo from the ‘40s. This leads them to believe that one of the charred victims in the car is actually Sally. That means Jerry the bartender is a liar. Actually, what it really means is that Jerry is Joe Flynn and his wife is Vera Mulqueen. Both are very much alive.
Stan Banks had figured out Joe and Vera’s secret. He threatened to expose them. Joe told him where to find the Blue Butterfly to avoid that. But he didn’t kill anyone. No, Stan was murdered by Frankie Hunsacker, the son of the woman who sold Joe’s diary to Stan. Beckett arrests this man who had been working for Joe and Vera to garner information on the Blue Butterfly, which was actually nothing more than costume jewelry. Case closed. Well, one case is closed.[break]
Castle and Beckett get Joe and Vera to tell them the true story about what went down the night they disappeared. They snuck into the alley during the prizefight to find Sally waiting for them with a gun. There was a struggle between Joe and this angry young woman’s hubby. BANG! Sally accidentally shot her husband dead. Then, in a struggle with Vera, Sally was also gunned down. Joe helped his true love plop the bodies in a car to burn them beyond recognition.
It was at that moment that Joe and Vera began a new life together without any help from the Blue Butterfly. Vera didn’t want to have anything to do with that cursed necklace. Joe didn’t want Dempsey to have it either. He hid in a wall outside the club. Neither of them ever went back for it even though they thought it was worth a fortune. They had each other. That’s all they ever needed.
Beckett knows what happened was self-defense, so no arrests are made. She does, however, wonder if they should have told the elderly couple that the Blue Butterfly wasn’t a million-dollar necklace. Castle says, “Why ruin it for them. No, that’s stuff dreams are made of.” Back in the ‘40s, Vera asks Joe to tell her he loves her. He responds “always.” They share a passionate kiss before heading off on their future together. Castle was right. It’s the stuff dreams are made of.