Gary is a thief that took Lo's idea of his disguise. Instead of protecting Lord Janna's maids, Gary uses his disguise for personal gain.
He is first seen taking an apple from Aphmau and putting it in his dress. He figured out she was trying to sneak into the wedding and called her a thief to cover his own intentions. He was eventually convinced to help Aphmau sneak in after she told him she could jus turn him in.
Gary is later caught pillaging by Aphmau. Some guards come in and tell them that they're in a restricted area. Lo then knocks out the guards with a frying pan and is surprised and annoyed to see Gary. Gary admitted that he was about to go back on his word and turn Aphmau in. Lo tells Aphmau that Gary is a thief and disguises himself as a maiden to steal stuff. Aphmau then calls back to the many times Gary called her a thief and was furious. Lo eventually knocked Gary out just as the guards woke up. Lo tells the guards that Gary knocked them out but he took care of him. The guards then arrest Lo.
Getting the last laugh, Gary rats out both Aphmau and Lo in exchange for his own freedom, foiling their plan of saving Hailey and almost getting them executed.