I Am the Cheese
This one's a toughie. The antagonist is the villain, and Mr. Grey is supposedly helping the Farmer family. But Shmoop can't get past a nagging feeling that he was actually out to get them, or was at least selfish enough to turn on them in order to protect himself. Did he have something to do with the murder of Adam's parents? We can't be sure, but just the fact that we're questioning it raises some concerns. The way Adam's dad describes Mr. Grey also leads us to believe he's the bad guy; he even says, "Sometimes, when he visits, we sit there like enemies" (25.13). While Adam's dad isn't the official Deemer-of-Antagonists (and neither is Shmoop), we tend to believe him since he's one of our few trusted characters.