Mr. Trilling was a dope dealer who met Dylan McKay while hanging out at a pool hall. He was largely responsible for getting Dylan hooked on heroin, recommending it to him if he really want to get high. After Dylan got high and crashed his Porsche, Mr. Trilling became worried that Dylan would turn him into the police. After learning from Valerie Malone that Dylan was in the hospital, he sneaked into his room and threatened him before Iris McKay interrupted and Mr. Trilling left.
Mr. Trilling was not seen in the series after that, so it is assumed Dylan did not mention him to the police.