Blizzard operates his criminal empire with impunity having bribed the local police force into turning a blind eye. But the Federal Secret Service has him in their sights. Their head, Lichtenstein (Milton Ross) asks his best operative, Rose (Ethel Grey Terry), to infiltrate the operation for incriminating evidence.
She is accepted by Blizzard, quickly becoming one of his favorites, even coming under his controlling spell. But when she discovers a secret passage down to the cellars leading to a completely outfitted surgical operating room (puzzling) and a large cache of weapons (alarming), she knows she has to report back.
Then ... She scribbles a note and throws it from a rear window to a Secret Service agent waiting outside.
... and Now, the scene above was most likely filmed on a studio set but this window is where it was meant to be - read on for its location.
Then ... the agent picks up the note but he is immediately attacked and neutralized by one of Blizzard's henchmen.
... and Now, he picked up the note in front of 7 Old Chinatown Lane (map). At left, note the building's standpipe; it's very similar to the one almost a century ago. The window pictured in the Now image above, at 9 Old Chinatown Lane, is typical of this building's 2nd story windows.
CitySleuth recognized the alley having previously researched a foot chase in the 1949 movie Impact which ended up (below) at #11 Old Chinatown Lane.
Here's a 1955 photo of Old Chinatown Lane, formerly Church Alley, viewed from Washington Street. Note that this is actually a block away from Wentworth Place where we previously learned that Blizzard's office is located. Directorial license prevails.
... and Now, a fire escape and utility equipment has been added on the left side but Old Chinatown Lane today retains its same character.
Blizzard now knows that she's a spy and she knows he knows when he hints that her number is up. But after commanding her to operate his foot pedals (hmm...) he is swayed by how well he plays with her help... "You're the best pedaler I ever had". Rose is spared.