Su Lin worries that if she is called to testify at Walter's trial she may harm his case and has laid low, but when she is spotted in the courthouse she takes off, closely pursued by Marsha.
Then ... Su Lin dashes from the Hall of Justice and across Kearny to the junction with Washington Street. Portsmouth Square plaza is over to the left and we see a night club advertising 'Dancing' at 720 Washington . She hustles across Washington and jumps in the cab parked outside the jewelry store . It makes a right and heads up Washington.
Marsha pursues Su Lin through several blocks in Chinatown. As the chase unfolds in the Then and Now images below, readers can follow along using the yellow arrows on this Google satellite map (click it to enlarge).
Below, (location 1 on the map) Marsha hails a cab ... "Follow that yellow cab!" ... (haven't we all wanted to do that?) and as it turns left into Washington we again see, to the north along Kearny, the Sentinel Building sign and the Shasta billboard seen moments before from inside the Hall of Justice. In the same view today, the top of the wall that carried the billboard is just visible above newer buildings. (Click anywhere on these images to enlarge them).
Behind Su Lin's Yellow cab on the Washington block (2 on the map) the trees of Portsmouth Square almost hide the Hall of Justice. Today, a Hilton hotel sits on the old Hall of Justice site. In both Then and Now pictures, below, the mid-span caisson of the Bay Bridge can be seen in the distance.
Marsha's DeSoto cab follows Su Lin south along the 800 block of Grant Avenue between Washington and Clay (3 on the map). The most glaring change between Then and Now ? ... the one-way traffic has been reversed.
In the next shot (4 on the map) we see them, still on Grant, crossing a junction but this is a cut-back to Washington, the cross street behind location 3 above. The bar on the corner on the left in the Now image is the Buddha Lounge at 901 Grant. Rita Hayworth crossed this same junction two years earlier when she chased Orson Welles through Chinatown in The Lady From Shanghai.
Location 5 is the same block of Grant as location 3, a little closer this time to Clay. The tapered pagoda sign up on the left marked the Chinese Pagoda restaurant at 830 Grant, now the Peking Bazaar just past the Empress of China sign below right. In both Then and Now images the distinctive pagoda rooftops of the Sing Fat and Sing Chong buildings stand out against the sky two blocks down the road at California Street.
The next shot (6 on the map) shows Su Lin's cab turning into Ross Alley from Washington Street - this chase is cutting back and forth with no regard to continuity. These pictures were taken 60+ years apart? Could've fooled me! Too, it's commendable that folks back then kept their streets looking tidy.
Su Lin leaps out of her cab and darts up a narrow passage connecting Ross Alley to the adjacent and parallel Old Chinatown Lane (7 on the map) - for some reason a gate now blocks this handy short cut. That's a rather revealing view of Marsha in pursuit as her form-fitting suit is stretched to the limit.
They emerge from the passage and Su Lin enters 11 Old Chinatown Lane and up a flight of stairs to her apartment (8 on the map). CitySleuth can only shake his head over the graffiti in the Now image, a modern-day phenomenon not seen in the 1940s.
Here's a closer look at 11 Old Chinatown Lane today. The ground floor is the shuttered office of Mabel Y. Kao, a long serving obstetrician in Chinatown who died in 2007 at the grand old age of 98 ... this remarkable woman was delivering babies in Chinatown in 1949 when this movie was filmed! The doorway on the right is the one Su Lin entered and through the window above it you can just make out the stairs she took to get to her apartment.
In the apartment (Su Lin's uncle's place, seen earlier in the movie) Marsha beseeches Su Lin to testify on Walter's behalf. Su Lin then remembers that Walter's wife Irene had gone out late the night that Torrence, her lover who Walter was accused of murdering, had died. This suggests Irene had pre-planned a rendezvous with Torrence, a contradiction of her evidence.
Marsha gets Lt. Quincy to track down Su Lin's tip and they find supporting information which leads to Walter's release and Irene's arrest for conspiring with Torrence to kill Walter. All ends happily ever after and the audience files out fervently hoping that Walter and Marsha go on to do the right thing.