Professor Quirrell (Ian Hart) is the one trying to steal the stone, not Snape (Alan Rickman). Quirrell's turban is hiding a disembodied Voldemort (Richard Bremmer). Harry (Daniel Radcliffe), with the help of Hermione and Ron (Emma Watson, Rupert Grint) is able to stop the two-faced wizard, and win the house cup for Gryffindor.
Thanks, Jocelyn G.! It sure is great to have family in Scotland!