She's just robbed money from her place of work and used it to buy a car and run away with her boyfriend. Tiredness overcomes her, and so Janet checks into the Bates Motel.

Thus, a drama becomes a horror as a man dressed as his own mother stabs her to death in the shower to a shrieking violin soundtrack.

It remains the most memorable scene of all, despite the use of chocolate sauce instead of blood, a stand-in for Anthony Perkins as he wasn't on set and not a single shot had both a knife and flesh in it. Genius.