Tracker's Biggest Mystery, Explained: A Complete Timeline Of What Happened To Colter Shaw's Father

For three seasons, "Tracker" has slowly unraveled the mystery surrounding Colter Shaw's father. What once seemed like a simple story about a paranoid man dying in the woods has since spiraled into something much bigger.

At this point, we know Ashton Shaw (Lee Tergesen) was tied to government contractors, secret research, and a mysterious Alaska facility that may have been conducting dangerous experiments. We also know Colter (Justin Hartley) spent years believing his brother Russell (Jensen Ackles) killed their father, while their mother, Mary (Wendy Crewson), quietly hid key pieces of the truth from both of them, as well as their younger sister Dory (Melissa Roxburgh).

Ahead of the hit CBS drama's two-part Season 3 finale — which reunites Hartley with Ackles and promises long-awaited answers about what happened to Colter and Russell's father — TVLine is rounding up everything we've learned piece by piece over the past 53 episodes.

Ashton and Mary Shaw were once respected Berkeley professors, but Ashton's work eventually drew him into the orbit of government contractors and a shadowy organization later identified as the Chrono Stasis Institute.

Over time, Ashton became increasingly paranoid, convinced dangerous people were watching him. For years, Colter believed those fears were symptoms of mental illness. But as the series progressed, evidence began to suggest Ashton may have had legitimate reasons to fear for his safety.

Recent revelations connected Ashton to a secretive Alaska-based research facility allegedly funded by DARPA, where experiments involving unexplained phenomena took place before a catastrophic "accident" shut the operation down. According to Buck Avery, whose family once leased land in the area to government contractors, Ashton was present when the incident occurred.

After the accident, Ashton uprooted his family from Berkeley and moved them to an off-grid compound near Sierra National Forest. There, he trained Russell, Colter, and Dory in survivalism — hunting, tracking, and climbing — while warning them that unnamed enemies were coming.

Over time, Ashton's behavior became more erratic and frightening, particularly from Mary's perspective. She ultimately decided to leave Ashton and sought help from local lineman Otto Waldron to escape with the children.

In 2003, Ashton fled into the woods during what Colter believed was another paranoid episode. Russell chased after him.

An hour later, Colter discovered Ashton dead at the bottom of Devil's Notch, and for decades, he believed his older brother pushed their father. Years later, Russell revealed there had been another man in the woods that night — someone he had previously seen speaking with Mary.

The Season 2 finale identified that man as Otto Waldron, who admitted he pushed Ashton during a confrontation. However, Otto stopped short of claiming Mary ordered Ashton's death outright, leaving open the possibility that events spiraled beyond anyone's original intentions.

After Ashton's death, the Shaw siblings scattered. Dory went to live with relatives, Russell left home at Mary's urging, and Colter stayed behind with his mother.

For years, Mary allowed Colter to believe Russell did, in fact, kill Ashton, while simultaneously urging him not to reconnect with his brother. But as more details emerged, it became increasingly clear that Mary had concealed critical information from all three of her children. Even Russell later admitted that Mary had lied to him, too.

The mystery deepened when family friend Lizzy Hawking (Jennifer Morrison) revealed that Ashton had secretly stored journals and research papers with her mother — a former colleague with whom he'd also been having an affair.

After her mother's death, Lizzy discovered the materials hidden in a box beneath her bed. But before Colter could examine them himself, Lizzy sent the box to Dory, who in turn concealed its existence from her brothers despite repeatedly urging Colter to move on from the past.

The journals eventually helped Colter uncover Ashton's ties to the Chrono Stasis Institute and an Alaska facility tied to the mysterious accident.

At this point, "Tracker" is no longer treating Ashton Shaw's paranoia as the product of a man simply losing his grip on reality. Instead, the series suggests he got tangled up in something far more dangerous involving government-backed experimentation, covert academic research, and buried institutional secrets.

The Chrono Stasis Institute, the Alaska facility, the mysterious accident, and the disappearance of Chrono Stasis Institute researcher Dr. Serena Jukic (Jeri Ryan) all point to a conspiracy that extends far beyond the Shaw family.

Answers will likely come in the two-part Season 3 finale, airing Sunday, May 17 and 24 (CBS, 9/8c). In Part 1, titled "Chrono Stasis," Colter and Russell "unite in a personal mission to uncover their father's mysterious work." In Part 2, titled "The Best Ones," the Shaw brothers "search for a victim of a nefarious research project," which presumably ties back to Ashton's life work. Are you ready for answers?