What Tumor Does Jensen Ackles' Character Have in Prime Video's 'Countdown'?

Prime Video’s Countdown got off to a rough start with the reveal that Jensen Ackles‘ character has a fatal health diagnosis.

During the premiere, which aired on Wednesday, June 25, Mark Meachum (Ackles) was seen suffering from consistent headaches. He visited a doctor, who revealed Meachum had already been diagnosed with a brain tumor nine months prior.

“With this aggressive form of glioblastoma multiforme, the risks of surgery or radiation outweigh the benefits,” the medical professional noted. “I will up the dosage of your medication and we will continue with regular MRIs.”

The doctor confirmed that Meachum’s health issue wasn’t curable, adding, “Why don’t you find a beach somewhere, put your feet up, take as much relief medication as you can and live out the time you have left with as much comfort as you can?”

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Meachum replied that he wished he “could” take a break. Instead, he spent the entire first three episodes of the season putting his body through strenuous activities while dealing with a drug cartel, a man posing a major threat to the U.S. and any other physical labor that came with working on a secret task force.

Countdown follows an LAPD detective who is recruited onto a covert task force of undercover agents from various law enforcement agencies after a Department of Homeland Security officer is killed in plain sight. The group must track down the murderer — but there is a larger conspiracy at work that they need to uncover while racing to protect Los Angeles.

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The Prime Video series is one of Ackles’ many projects, as he continues to be booked and busy after becoming a household name with The CW’s Supernatural. Ackles, 47, who played fan-favorite Dean Winchester for 15 seasons, has since starred on The Boys and will now be at the center of his own prequel series: Vought Rising.

Ackles also had a guest spot on Big Sky and produced The Winchesters before his recurring role on Tracker as Justin Hartley‘s onscreen brother.

“I had an incredible experience working with the Prime Video team on The Boys and am delighted to be able to continue that relationship on Countdown,” Ackles shared in a 2024 statement. “I simply cannot wait to partner with Derek [Haas] and the rest of our Countdown family to bring this story to life.”

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Countdown also stars Eric Dane, Jessica Camacho, Violett Beane, Uli Latukefu and Elliot Knight. It is one of Dane’s new projects in the wake of his ALS diagnosis.

“I have been diagnosed with ALS,” Dane, 52, said in a statement in April. “I am grateful to have my loving family by my side as we navigate this next chapter. I feel fortunate that I am able to continue working and am looking forward to returning to set of Euphoria next week.”

The statement continued: “I kindly ask that you give my family and I privacy during this time.”

New episodes of Countdown air Wednesdays on Prime Video.