At about 9:25 p.m. on Monday, a 26-year-old woman was riding the CTA Blue Line train near Clark and Lake Streets when she got in an argument with a man believed to be 45 years old. The altercation escalated and became physical, police said, and the man poured a liquid onto the woman and ignited it, setting her on fire. The train then came to a stop and the man fled the scene, police added. A person of interest was taken into custody. Police did not offer additional information on the person of i