Want to know how it started?
This is how the Supernatural series all started:

Sam Winchester is a college student bound for law school, determined to
escape his family's past - unlike his older brother, Dean. Ever since
they were little their father has been consumed with an obsession to
find the evil forces that murdered his beloved wife, in result
recruiting and training his two young sons to help him in revenge. They
have grown up as hunters of the supernatural. Sam escaped under the
premise of going to college, and now has a happy life with his
girlfriend, Jessica, and a promising future career. Dean, however,
stayed behind with his father to join him in his "hunting".
Dean goes to Sam for help when their father goes missing. Now Sam must
join his brother to find him. His one weekend trip to search for the
missing John Winchester becomes an ongoing quest after a horrible
tragedy ruins any thought of a happy life for Sam.
The two brothers, bound by tragedy and blood to their mission, travel
across the country encountering terrifying and dangerous forces most
believe to be nothing but superstition and folklore, such as the Lady
in White, the Indian beast known as the Wendigo, Phantom Travelers who
cause plane crashes, Bloody Mary, vampires, demons and many more.
there has been 5 seasons so far.