seek the old man . . . win him to my party
This not only makes sense in the context of the De Laceys' civilized demeanor, which for many months now has served as the Creature's behavioral model, but also specifically in respect to the elder De Lacey's explicit understanding of the dynamics of alienation just witnessed in the Creature's night-time rampage. The use of political terminology reminds us of the Creature's reading matter (particularly of the education furnished him by Volney's Ruines), but also suggests that he still thinks it possible to negotiate a place for himself within the human polity.