Time really is a flat circle on "True Detective."
An eagle-eyed fan noticed an Easter egg in HBO's preview for Season 3, Episode 5, "If You Have Ghosts," which airs February 3.
In the 2015 timeline, Detective Hays (Mahershala Ali) is getting interviewed by Elisa Montgomery (Sarah Gadon), an investigative filmmaker who is working on a true crime documentary about the Purcell case from 1967.
The promo for Episode 5 (around the 19 second mark) shows the screen of Elisa's laptop, which displays an article with the headline "Former State Police Officers Stop Alleged Serial Killer" and pictures of Detectives Rust Cohle (played by Mathew McConaughey) and Marty Hart (Woody Harrelson) — the protagonists from "True Detective" Season 1.
So, the two seasons exist in the same universe! Hays is being interviewed about three years after the modern-day timeline of Season 1 (which took place in 2012).
This isn't the only Season 1 Easter egg in the new season. In Episode 2, Elisa said, "It's been theorized that the straw dolls are a sign of pedophile groups, like the crooked spiral."
The straw dolls are clues found by Hays at the Purcell crime scene. The crooked spiral is a sigil repeated throughout Season 1, notably carved onto victim Dora Lange's back.
It's unlikely there's a deeper connection, and that these Easter eggs just indicate that the two seasons take place in the same universe. But it's still interesting to speculate about whether Rust or Marty might show up to lend their expertise on finding creepy serial killers.