run off and leave him NOT holding the bag

To not only skip out on your partner in crime so dat he gets da blame for your "combined" transgressions, but you also abscond with whatever ill-gotten booty dat said hapless cohort helped you to "acquire"!

In da "Adventures Of Huckleberry Finn" tale, da King and da Duke had both secretly planned to bilk da other out of da sack of gold --- i.e., each one of said selfish 'n' shameless shysters possessed da classic "no honor among thieves" mindset, and thus was going to pull da disgraceful "run off and leave him NOT holding the bag" on his unwitting accomplice!