On this page of our guide to BioShock Infinite you will find the first part of a detailed walkthrough of Chapter 24 - Finkton Proper. On the way back to the workshop of the gunsmith, Booker can gain new vigor called Charge. Take part in new battles in the vicinity of Plaza of Zeal.
Start off by exploring an office that previously had an inaccessible storage area. This time you won't have to worry about the bars blocking your way and as a result you'll be allowed to collect a new vigor - Charge. This vigor will make you much stronger in close combat.
The only way to return to the workshop is to fight your way through the bridge in the Plaza of Zeal. Don't forget to use the tears to your advantage, especially since they weren't here before. The enemies will remain in similiar strength so you should know what to expect.
Once you're at the plaza use the fact that the Vox are engaged in battle with the police and quickly make your way to Chen Lin's workshop. You'll find a corpse of Lady Lin here and also make sure to examine a nearby shelf to find Voxophone #50.