[2] Harold Bledsoe, a student of botany, is traveling by rail to San Francisco, where the captain of police has sent for him to help investigate a crime wave in the city's "Chinatown" district.

Also traveling to the city, but by car, are a young woman named Billie Lee and her little brother Buddy, who needs his lame leg treated in San Francisco by "the famous Chinese physician" Dr. Chang Gow.

Harold does not recognize Billie as the woman on his photograph, in fact, he thinks she is a boy since she is wearing a man's cap and overalls to work on the engine.

He causes chaos at the station for the next two weeks by using the messy, fine black powder to take fingerprints of everyone at the building, including the print of a visitor, John Thorne, a respected citizen who is pressuring the police to crack down on crime.

Harold's antics continue to anger staff at the station, so the desk sergeant hatches a scheme to get rid of him and sends him on a mission to find the "Dragon," the mysterious master of the city's Chinese underworld.

Aware of their presence, employees there set up a series of spooky effects to frighten them from the premises, yet Harold and Clancy remain despite being terrified.

He is mortified until he notices in a mirror that in his fight with the Dragon, the drug lord had left his sooty fingerprint on Harold's forehead, and it matches Thorne's print.

In its October 3, 1929 issue, the popular New York-based trade paper The Film Daily reports the following about the release and premiere of Welcome Danger.Harold Lloyd is scheduled to arrive in New York [City] Monday to attend the world premiere of his latest Paramount release, "Welcome Danger," opening at the Rivoli Theater, October 12, according to telegraphic information received from Hollywood today.

Many reviewers at that time, in addition to expressing their opinions about a movie's plot and production values, provided readers with their initial impressions after hearing an actor actually speak on screen.

When the big comedy sequences begin to build up and he goes hectic with his pantomime and slapstick his voice arises to the occasion and the audience will be likely to forget or overcome any disappointments over it in other spots...Recording is generally satisfactory, and Miss Kent is an attractive opposite to Lloyd.

[6][7]Walter R. Greene, however, a reviewer for Motion Picture News in 1929, complimented Lloyd's stunts in Welcome Danger as well as the tone and general quality of the comedian's voice.

"Harold Lloyd", Greene wrote, "has nothing to fear from talking pictures," adding "His voice registers excellently, and there is personality in its reproduction.

"[8] On February 21, 1930, the first day of its release in China, the film sparked outrage among 35 viewers who, in their anger, wrote to Shanghai's Republican Daily News.

He left the theatre in protest when a scene showed Harold Lloyd throwing money on the ground to a Chinese flower seller.

Before the next screening, Hong returned to the theatre to give a speech, condemning the film's offensive portrayal of Chinese people and urging the audience to boycott it.