When Morse says "I was meant to pick up the knife! It's handle was toward my hand", and McNutt replies "You can leave out the literary flourishes, Morse", the reference is to the dagger speech in Shakespeare's play, Macbeth:
Is this a dagger which I see before me,
The handle toward my hand? Come, let me clutch thee -
I have thee not, and yet I see thee still!
Art thou not, fatal vision, sensible
To feeling as to sight, or art thou but
A dagger of the mind, a false creation,
Proceeding from the heat-oppressèd brain?