Now we have new information tonight in the death of cory monteith, the compelling star of the hit show "glee," singing the sweet songs but battling heroin addiction. He recently tried rehab. Abc's... See More
Now we have new information tonight in the death of cory monteith, the compelling star of the hit show "glee," singing the sweet songs but battling heroin addiction. He recently tried rehab. Abc's neal karlinsky tells us some time after rehab your body can be at even greater risk. Reporter: On what would turn out to be the last plane trip of his life, "glee" star cory monteith recorded this video for a fan. Stay out of trouble, and stay in school. Reporter: Co-star jane lynch, on the "tonight show" overnight, offered her own version of what so many have said -- monteith was a humble man with a big heart. He once flew across the country on his own nickel to meet with a sick kid whose last wish was to meet him. You know, that's the kind of guy he was. He was a real giver. ♪ Just a small town girl, living in a lonely world ♪ Reporter: So what went wrong? How could the 31-year-old, who just put himself into rehab in april, overdose with no warning signs? Just because somebody has gone through 30 days in rehab, they're not safe Reporter: Strange as it sounds, dr. Mitch rosenthal says the period immediately following rehab is often the most dangerous. They are vulnerable from a physiologic point of view because the drug that they took 30 days ago at that dose level can kill them 30 days later. ♪ Why should we worry ♪ ♪ no one will care, girl ♪ Reporter: For those trying to get clean, the pull of addiction is always there, even if sometimes it's hidden behind a friendly smile. Neal karlinsky, abc news, seattle.
This transcript has been automatically generated and may not be 100% accurate.