Indiana State Police have issued a silver alert for a missing adult from Plainfield. Morgan M. Johnson was last seen May 18 near the Interstate 70 exit. The 27-year-old is described as 5 feet, 8 inches tall, weighing about 155 pounds, with black hair and dark brown eyes. He was last seen wearing blue jeans, a sweater and a black leather jacket. Investigators say Johnson may be unable to communicate due to lack of needed medication. He is believed to be driving a 1995 four-door Pontiac Grand Am with Indiana license plate JS1830.