First seen in the inaugural episode “The Long Bright Dark,” etched into the back of murder victim Dora Lange, the spiral symbol shows up a few more times throughout the first season of “True Detective,” doubling as a motif for the Carcosa cult and the show’s preoccupation with the nature of recurrence and time being a “flat circle.”
In episode 3 “Seeing Things,” we’re introduced to Errol, who became known as “Lawnmower Man” among fans, due to the fact he’s shown riding a mower on the grounds of an abandoned Christian academy. Then, Rust and Marty spent the next four episodes chasing down leads before seemingly solving the case by killing drug dealer and Errol’s co-conspirator Reggie Ledoux (Charles Halford).
But as episode 7 “After You’ve Gone” draws to a close, Errol, once again astride his infamous mower, reappeared when detectives Thomas Papania (Tory Kittles) and Maynard Gilbough (Michael Potts) stopped to ask him directions. After the detectives left, a wide shot of Errol revealed he’d been mowing the turf at a cemetery in a spiral pattern.
Everyone from Reddit sleuths to Entertainment Weekly was struck by this detail, which when coupled with Errol’s ominous delivery of the line, “My family has been here a long, long time,” basically confirmed he was indeed the “monster at the end of the story,” as Rust put it. But it seems neither Nic Pizzolatto nor Cary Fukunaga planned on including this Easter egg until the day of shooting. In fact, the fastidious Pizzolatto has his director to thank for this particularly subtle yet effective detail.
Source : https://www.slashfilm.com/1297304/true-detectives-season-1-flat-circle-easter-egg-happened-on-fly/