Kirk, Spock, McCoy, Scotty and a Female Redshirt catch a space disease that causes rapid aging. Chekov doesn’t (because he was scared at the time of infection — hence the cure, much like for the hiccups, is shouting “boo” at the afflicted.) As the obscenely bad makeup gets worse and worse we see our heroes getting older. Kirk is forgetful, McCoy is grouchy, Scotty is just tired. A visiting Commodore puts Kirk on trial to relieve him of his command (third time by my count.) But even with his youth and intellect, he can’t controll a Starship with his “desk mentality!!!” Luckily the cure comes just in time for Kirk to save the ship from Romulans (but not the Redshirt from disease — even though she was clearly the youngest-looking of the infected.) A fun episode — though, I must admit, a little dark and heavy at times.