In 'You're Not You,' a film adaptation of Michelle Wildgen's 2007 novel of the same name, out October 10, Emmy Rossum plays Bec, an aspiring musician who becomes the unlikely caretaker for Kate (Hilary Swank), a cultured (and cultivated) woman with quickly progressing ALS. It's a timely topic, of course, seeing as ALS—also known as Lou Gehrig's disease—has captured our country's attention and compassion thanks to the now-viral ice bucket challenge. But as Rossum, who lost a good friend to another terminal illness while filming 'You're Not You,' knows, the cruelty of ALS, a neurodegenerative disease that can completely paralyze its victim's body while leaving brain function intact, is hard to grasp. Here, in her own words, she recounts what it was like to get up close and personal with the disease:

In my life, I have always been very scared of sickness, aging, and death. So it's interesting that I got involved with You're Not You at the tail end of losing a good friend to melanoma. My friend, who died before we even started shooting, went into hospice—she'd stopped treatment and had tumors so big you could feel them through her ribcage—the same day I auditioned for the movie. I was so broken open that day that I'm sure it only added to my performance.

At its core, You're Not You is really a love story—a non-romantic love story between two women, which can be the most intense, pure form of friendship. The only good thing about terminal illness is that it removes all of the pretense so that two people can cut right to getting to know each other in the most human way: taking care of each other both physically and emotionally.

Recently, there's been a spotlight on ALS—and there's somewhat of a 'cool factor' to completing the ice bucket challenge. Of course, we want to see our favorite CW stars in their bathing suits pouring ice water over their heads—I want to see that, too! But, ultimately, ALS is still a disease very few people actually understand or know about.

Hilary and I spent three weeks preparing for our roles by meeting with people who have the disease. I did a lot of research on what it actually does to the body, and how it can progress in different ways. (For example, if it starts in the vocal cords, it's probably going to progress more quickly.) But more than its physical manifestations, I zeroed in on how ALS can affect someone's mental health. As part of my research, I spent time with a man who used to be a big-time lawyer. When I spoke to his son—the dad was pretty late into his illness—he told me, "Just six months ago he was running the office." When I met with him he had a ventilator in his neck; he couldn't speak, couldn't walk, couldn't move. He was completely reliant on other people. If it weren't for his muscles shutting down on him, he could have still practiced law, been a good father, and functioned as a member of society. When you have ALS, you are trapped in your own body as it's shutting down. The cruelty of that is still hard for me to understand.

At the very end of her struggle with melanoma, my friend told me that she wanted to go skydiving, meet Dave Matthews, get stoned, and eat Chinese food at my pool before she died. And that's kind of the stuff we did. On the day she died, she was surrounded by her family and people that loved her.

Her story is terribly sad, but it's also uplifting. A lot of us will spend the next forty years of our lives doing a bunch of stuff we don't really love. If we were told that we had two years to live, maybe we'd actually do what we really want to do—even if that just means getting stoned and eating Chinese food! At the end of the movie, Kate and Bec end up doing what they really want: Bec wants to matter to somebody; Kate wants somebody to live the life that she always wanted—one that's messy, sure, but also full of art and fulfilled dreams.

In the end, they get the one thing that really matters: each other.

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