The horrid mystery hanging over us in this house gets into my head like liquor, and makes me wild.

Gabriel Betteredge speaks these lines in Chapter 17 of the First Period. The motif of intoxication runs through the first period and infects various strands of the plot. The intoxication can arise from the Moonstone itself, in whose depths one loses oneself. The intoxication also arises from the mystery surrounding the Moonstone. Gabriel proclaims that he has "detective fever" and other members of the household (such as Rosanna) react as though their mind obeys an outside force, such as "liquor." Gabriel's insistence that the liquor- like effect makes him "wild" highlights a sub-theme—The Moonstone seems to propose that people obey their natural, or subconscious, instincts when under the influence of a substance.