Title is from Macbeth, Act 2 Scene 3, in which the porter says: "Knock, knock! Never at quiet. What are you? But this place is too cold for hell. I'll devil-porter it no further..."
The names Kate Minola and Bianca reference the two sisters from Shakespeare's "Taming of the Shrew."
Silas Yorick is the name on the grave where Billy the Brick leaves the urn. Yorick is the dead court jester whose skull is exhumed by the First Gravedigger in Act 5, Scene 1 of Hamlet.
DI Marlowe mentions Richard Hurd murdering Teddy Shrewsbury- a nod to Richard III and the supposed murder of the princes in the tower, King Edward V and Richard of Shrewsbury.
About midway, as Lu & DI Marlowe are leaving the Shakespeare & Hathaway office, Sebastian recites lines from William Shakespeare's Henry V, "We few, we happy few, we band of brothers; For he to-day that sheds his blood with me Shall be my brother; be he ne'er so vile, This day shall gentle his condition."