Watch Bombuj. 'Knock Knock' tells the story of down-on-his-luck former boxer Sam Grant, who one night finds himself caught in a whirlwind of conjecture and conundrum as his colorful and quirky neighbors come to him with scary tales of their apartment's mysterious new resident. Inspired by the retro horror classics of VHS days gone by, 'Knock Knock', is sure to be a treat for any horror fan and aficionado.