We were driving on Commonwealth Ave when the Boston Fire Alarm office keyed the radio saying, "In District 11, striking box XXXX for 1297 Commonwealth Ave for a reported building fire". We looked for an address on the nearest apartment complex...DAMN we were at 375! I did a not so quick u-turn and headed in the opposite direction. Red lights, traffic, and pedestrians all slowed the response. The first in companies reported nothing was showing on arrival. The chief took command, and after a 5 minute investigation, he radioed to have incoming companies use caution. He then canceled the RIT and Rescue 1. Then, all of a sudden a portable radio reported smoke in an apartment and to KEEP EVERYONE COMING! We arrived and found no place to park...AT ALL. I took a a side road which lead to an alley and then we arrived to the rear of the building that the companies were investigating. Smoke was pushing from Side C which was found to be plastic left on a hot stove top. Companies were placed in service shortly after hose line pick up.