Three years after Cory Monteith's unexpected death at the age of 31, a new TV special digs deep into the Glee star's final months before he overdosed from a mixture of heroin and alcohol.

In a promo for Autopsy: The Last Hours of Cory Monteith, actors reenact the Canadian's tense meeting with showrunner Ryan Murphy over his substance abuse issues.

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“Cory was late several times for work and people began sensing from the smell of his breath, that there were problems," media journalist James Desborough explains. "We understand from sources that at times he would neck bottles of whiskey in just under an hour.”

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Cory and Glee costar Lea Michele in 2011.

Cory, who played Finn Hudson on the hit series, missed the last two episodes of Season 4 because he was in treatment for the addictions.

He passed on July 13, 2013, before production on Season 5 began. His former girlfriend and costar, Lea Michele, recently paid tribute to her ex on Instagram.

"We may not have gotten to share a lifetime together.. But the memories.. they're the best of my life.. Love you Cory," the brunette beauty wrote.

Scroll through the gallery below to see what the rest of Cory's Glee castmates are doing now.