City companies sent on Box 1-2 to 47 N. 12th Street in "The Gut" for a structure fire. Units on location with with a working fire in a vacant, 3 story, duplex. An interior attack was initiated on a fire in the basement. A firefighter who fell through the first floor was assisted to safety. The evacuations tones were struck and a first alarm requested. Crews made a good knock on the fire keeping fire damage to the building of origin. Companies remained on the scene mopping up for about about 2 hours.