Police are looking for a man they say wore a mask and brandished a knife during a robbery at a Lisbon Falls convenience store. Detective Bill Tapley says the suspect entered the Big Apple store at about 11:30 p.m. on Wednesday, showed a knife and demanded cash from the clerk. Police tell The Times Record, the suspect left the store on foot with an undisclosed amount of cash. No one was hurt. The suspect was described as a white male possibly in his early 20s, approximately 5-foot-6-inches to 5-foot-8-inches tall, weighing between 150 and 160 pounds. He was wearing a black hooded sweatshirt and blue jeans and his face was covered by a gray mask.