SPOILERS for those who haven't watched or read 'Harry Potter and the Chamber of Secrets'
In Harry Potter and the Chamber of Secrets, it is revealed that the Chamber of Secrets has been opened at Hogwarts. The Chamber of Secrets was rumored to be a secret chamber created by Salazar Slytherin, one of the co-founders of Hogwarts, who believed only pure-bloods should be allowed into Hogwarts. His heir would return to Hogwarts and open the chamber and release some sort of monster. This monster would go around the school, attempting to kill as many muggle borns as it could, being controlled by the heir.
We later find out that Tom Riddle (a.k.a. Voldemort) is the heir of Slytherin, after previously opening the Chamber while he was at Hogwarts and using it to kill a muggle born. This time, he had preserved a piece of his soul in a diary and the diary had been given to first-year Ginny Weasley.
The piece of Tom's soul that was in the diary puts Ginny in a trance and he makes her order the monster to kill muggle borns (and for some reason, Filch's cat), with Ginny not knowing she was doing it.
However, this monster only manages to petrify its victims. It never actually kills the muggle borns even though that is its goal.
Eventually, Hermione gets an idea of what the monster may be. She goes to the library and finds a page that gives her the answer. However, before she can give the information to Harry and Ron, the monster petrifies her.
Eventually, Harry and Ron find the crumpled-up page in her hand. It was about a type of snake/monster called a basilisk that killed its victims just by looking at them in the eye. But the reason why no one was actually killed is because they didn't look the basilisk directly in the eye.
I would've put a picture of the basilisk here, but its appearance is too scary for a PG movie. But then again, this isn't a PG movie. I don't care, kids could be reading this.
Mrs. Norris (a cat, why did the basilisk petrify a cat?) only saw the eyes in the reflection. Justin Finch-Fletchley saw the eyes through Nearly Headless Nick, a ghost that was already dead. Colin Creevey saw the eyes through his camera. And Hermione had used a mirror to make sure to check behind her in case the basilisk was there. And Hermione had also written on the page that the basilisk was traveling through pipes.
But here's a theory:
What if Hermione didn't get the page from a library book? What if she got it from somewhere else?
I mean, think about it. Isn't it a little bit out of character for Hermione to borrow a library book, rip out a page, and vandalize it? I mean, she is a bookworm that loves reading and getting good grades. She also hates getting in trouble and breaking the rules.
So, why would she do that? Exactly. She wouldn't. So she had to have gotten the information from someone else.
Well, in the movie adaptation, while Draco is in Flourish & Blotts, he rips out a book page.
He then crumples it up and puts it in his pocket.
What if that was the page Hermione finds?
The theory states that Draco Malfoy saw Hermione in the library and he put the page on the table where Hermione could find it.
Okay, calm down.
You're probably saying that it is out of character for Draco Malfoy to give Hermione the sheet after calling her a Mudblood and clearly wanting Hermione and all other muggle borns dead.
But let's connect this to Snape. Severus Snape (portrayed by the late Alan Rickman) is a person that Voldemort and his Death Eaters believe to be a follower of Voldemort. However, inside, Snape is actually working for Dumbledore. What if this is the same for Draco Malfoy? What if Malfoy was a Mudblood-hater on the outside, but was actually concerned about the safety of others deep inside?