Miss Fisher's Murder Mysteries' cold open is very dramatic. A hotel concierge, Frank, is pushed off the roof, bag in hand, by a man demanding money (Colin Moody), as a maid, Enid (Michala Banas) searches below for something he dropped down the chute. Back home, Phryne is a little disturbed. She can't find her Mauser, but Butler reminds her she took it with her on her last trip, so it's still in the overnight bag. Aunt Prudence pops by to say she's had a telegram from Phryne's mother Margaret, begging for money, Phryne insists she forced her father to wire cash before sending him off to England.
Jack: But seeing that Fisher the Elder seems more resourceful and unpredictable than Fisher the Younger, how can I investigate this case without you?
Jack calls, asking her to come to the Hotel Grand. The bag Frank was holding is the overnight bag she couldn't find, taken from the hotel safe, which owner Hilda Cobb (Nell Feeney) confirms is only supposed to be open during business hours. Phryne realizes there's only one reason it could be in there: Baron Henry. Indeed, Phryne's father is not on a boat back to England; he claims to have missed it. (He did not miss the boat, she saw him board it.) Instead, he's drunkenly palling around with Enid. Phryne is livid. He never wired a dime to her mother. It's her money stolen, along with her gun. As she and Henry get into a row over it, Frank's nameless murderer returns, announcing he's there to fix the telephones. (He just cut the wires himself.)
As Enid brings down "tips" from Henry's room, Hilda mutters about his gambling. Dot attempts to inch closer, only to have Martin block her way. Jack and Fisher head to the roof, where Fisher realizes the contents went down the laundry chute, and she follows them, the old school way. At the bottom, she finds several bills Enid failed to rescue. Cobb insists this is a decent hotel, but Jack notes it's been raided for gambling. As Jack and Phryne confront Enid in the hall, Frank's murderer searches Henry's room, stealing his passport and finding Fisher's card.
Enid admits she went to Henry's room "as a shoulder to cry on" after losing all money gambling. Enid knows more than she's saying though, the expensive necklace she's wearing, and the bundle she pulls from a cabinet and runs off with says so. Unfortunately, the murderer seems to have seen her. Cobb insists she knows nothing about the gambling in her establishment. Still, the ledger Dot and Martin find in the back of her guest book says otherwise, and gives a name to who Henry played against, Karol Valenski (Goran D. Kleut), who Fisher and Jack find upstairs with his assistant Tomas (David Macrae), trying to throttle Phryne's father.
Valenski confirms Henry lost and promised to pay in the morning. Phryne thinks Henry robbed the safe to keep from paying. Jack is surprised, but Fisher tells him she once saw her father argue with a man who turned up drowned the next day, so it's not the first time she's suspected it. Dot sneaks in to see what she can find with Martin on lookout and turns up a box in a locked drawer. They're almost caught, so Martin starts making out with Dot, much to her shock.
The box seems empty, but Martin merely took the evidence to look good in front of Jack. Instead, Jack throws them back at Martin, pointing out Dot and Fisher's methods are not the cop's methods and forcing him to return them. They're love letters from Frank to Hilda, which break things off right before his death. Fisher and Dot gather up Prudence to hit up the weekly Twilight Waltz at the hotel to see what they can find. Dot gets Cobb to teach her the waltz so Fisher can go snooping, as Prudence awaits Henry, to offer him whatever amount of money it takes to make him disappear. As she dances with Dot, Cobb admits Frank dumped her because she was too old, so she fired him.
Fisher is caught in the gambling room by Frank's murderer, still using the phones as his excuse. He has keys to every door, though, which Fisher uses to unlock a room set up for spying on Karol's opponents and communicating them through morse code. Cobb insists it was all Frank's idea; she went along because she was desperate to keep the hotel going. Knowing how the cheat works, Fisher challenges Valenski to cards to win the IOU her father signed and the rest of the gambler's money. Enraged, Valenski finds Henry and throws him against a wall, only to have Henry produce Fisher's missing gun and tell him to buzz off.
Henry discovers Enid packing in her room. He begs her to go out one last time; Enid says she'll be down in a moment. As she escapes down the back stairs, Valenski follows her. But when Fisher sees her being accosted, it's Frank's murderer. The man runs, but Fisher gets the case and Henry's money. When Fisher and Jack return to the hotel, Henry has left with Bert and Cec to challenge Valenski to pistols at dawn for Enid's murder. Phryne arrives in time to stop it, telling her father of the mystery man.
Fisher knows her father too well and realizes he's terrified of whoever this is. Jack shows her the man who died was not the one she saw confront her father, and Phryne realizes the man following him is the same one she saw that night. Meanwhile, back at her house, Dot is trying to tell Martin there's no chance she'll leave Hugh for him when the nameless man walks in and kidnaps her. He also has Prudence call Phryne to return home immediately, just as Martin realizes Henry slipped out while he was crying down the phone over Dot's rejection.
Phryne arrives to find Butler, Dot, and Prudence tied up, and the nameless man there to rob them. She tells him she remembers him from the visit he paid to her father and demands an explanation. He refuses as Jack jumps him, knocking him into a marble table head first. He winds up in a coma. Fisher confronts Henry, demanding to know who this man is, but her father lies. Frustrated, Fisher has Bert and Cec take Henry away to Lillydale, to stay put until the next boat to England.