‘Tracker’: Jensen Ackles Returns for Final Season 3 Episodes — See Photos

Tracker Season 3 is being bookended by two-parters reuniting the Shaw brothers. Rewardist Colter (Justin Hartley) will once again be working alongside his brother, Russell (the returning Jensen Ackles), this time on something very personal to both.

Ackles first returns in the Sunday, May 17, episode, titled “Chrono Stasis,” the name of the institute that had been conducting experiments up in Alaska where their father visited months before his death. CBS teases: “Colter and Russell unite in a personal mission to uncover their father’s mysterious work.”

The network has also released photos, which you can see below, offering a look at Colter and Russell’s investigation along with guest stars Jeri Ryan as Dr. Serena Jukic and Jerry Trimble as Paul.

Buck Avery (Michael O’Neill) had told Colter about Serena in Episode 18. She was a research who mentioned an accident that happened at the Chrono Stasis Institute a month before the research facility was shut down. The Shaws’ father had been up there when that incident occurred, but Avery didn’t know what he was up to. Serena was deep in whatever was going on there, but she was not going to be easy to find, he warned Colter, who then passed along the name to Russell. It seems likely that Russell, using his contacts, successfully found her, leading to this team-up.

Ackles is also back in the May 24 Season 3 finale, “The Best Ones.” According to CBS, “Colter and Russell search for a victim of a nefarious research project.” Something tells us that’s related to the accident that occurred. But how will this all be connected to their father?

Scroll down to check out the photos from Season 3 Episode 21, “Chrono Stasis,” then head to the comments section with your predictions about the last two episodes.

Tracker, Sundays, 9/8c, CBS