Plot

Returning from European exile where she avoided testifying against her criminal associates, a former singer with a tell-all diary is murdered to ensure her silence.

Billie Bronson secretes a package in the trunk of Charlie Chan aboard a New York-bound transatlantic liner. Chan and his number one son, Lee are met at the pier by Inspector Nelson and two rival reporters, Joan Wendall and Speed Patton. Billie, having left the country hurriedly a year ago when sought as a material witness in a political scandal, has returned to "blow the lid off the town." She follows the Chans to their hotel and attempts to regain her package from the trunk, only to be interrupted by Lee. She then goes to the "Hottentot Club", where "candid-camera night" is in full progress, followed by Lee. Already present are Joan and Speed. Billie is mysteriously murdered and Charlie is summoned from a police banquet in his honor. Present in the room with the body are club manager Johnny Burke; club dancer and Burke's girl-friend Marie Collins and the two reporters. While seeking a motive for the murder, a second killing is discovered in Charlie's hotel room, the package is missing from Charlie's trunk and it is realized that it must have contained her diary. Charlie neatly puts together a few scattered clues and names.......as the killer.—Les Adams <longhorn1939@suddenlink.net>

On an ocean liner approaching New York, a man unsuccessfully tries to steal a small package hidden in a woman's stateroom. The woman then hides the package in the room next to hers, which belongs to the celebrated Honolulu detective Charlie Chan and his son Lee (returning from Germany after their previous adventure in 'Charlie Chan at the Olympics').

In New York, newspaper reporter Speed Patten slips into a taxi cab with the woman, whom he knows as Billie Bronson, and she promises to meet him at her hotel at midnight if he will keep quiet. As Speed reports the potential story to his editor Murdock, Murdock gets a call from Billie, who demands twice the amount he was willing to pay one year ago, and he sets up a meeting with her that night. Billie then bribes a bellhop for a key to Chan's room. As she tries to enter, Billie is spotted by Lee, and he follows her to the Hottentot Club, owned by racketeer Johnny Burke. There, mobster Buzz Moran warns Billie to get out of town before morning, after which she goes to Burke's office.

Meanwhile, Speed, who has come to the club with photographer Joan Wendall, follows Burke to meet Billie. Billie accuses Burke, her former lover, of giving her the "runaround" because of his involvement with Marie Collins, a dancer in the club, and pulls a gun on Burke as Marie opens the door. Later that day, Inspector Nelson gets word that Billie has been killed and that Lee is being held as a suspect. Nelson orders Lee's release and questions Speed, Burke, Marie and Joan.

At the crime scene, Chan notices that a napkin placed over a tray is not in a photograph which Joan took at the time of the murder. Just then, Louie, Burke's man, turns out the lights, and during a scuffle, Burke escapes. When the lights go on, Chan reveals that the key to his hotel room, which is present in the photograph, is now missing along with the napkin. Chan, Lee and Nelson return to Chan's room, where they find that the man on the boat who tried to rob Billie has just been killed. Marie then enters and recognizes him as her husband, Tom Mitchell. On the floor, Chan finds a crumpled page of a diary, which, he realizes, Mitchell was after. Chan finds Murdock in Billie's room, and Murdock explains that he was waiting to buy Billie's diary, which has information on racketeers and politicians in the city.

The next day, after reading Speed's newspaper account of the murder, Moran confronts Burke. After Burke knocks down Moran, Moran shoots at him and misses. With his lawyer, Burke goes to police headquarters, where a para-fin test to determine whether there are traces of gun powder on his hands proves to be negative. Chan reminds Nelson that the napkin may have been used to cover the gun and warns Burke that he is still investigating him. When Burke finds Lee in his room trying to reconstruct the murder, he gives a black eye to Lee, who hits him back before being thrown out. Burke tries to leave town, but he is apprehended at the airport, along with Marie, and taken back to his office, where Murdock and Moran are also brought.

Chan, Lee, Speed, Joan and Nelson also arrive at Burke's office, where Chan reveals that Mitchell was trying to get Billie's diary to ruin Burke, who stole his wife. Murdock then shows a page from the diary, which says that Speed used his newspaper job as a cover for blackmailing. Speed calls the page phony, and Chan accuses him of murder. Chan explains that he first suspected Speed when his newspaper account mentioned that Billie was shot in the back, a fact known only to the police and the murderer. Chan also reveals that he and Nelson planted the phony diary page to draw Speed out. Speed pulls a gun and confesses that he killed Billie because she was going to the district attorney with the diary, which implicated him. He then found Mitchell with the diary and killed him. He is about to shoot Chan when Lee jumps him. In the struggle, Speed is disarmed, while Lee gets a second black eye.