Sadie is tending to Zia and Amos while Carter confronts Set, he is in his avatar form.
Sadie teleported Set, the pyramid and Carter to the Washington monument
Carter is fighting with Set while Sadie reads out the incantation to destroy/banish Set from the Mortal world and into the Duat
Sadie stopped reading the incantation because she saw Set's chaos forming a serpent form in the air. Face Of Horror appeared in front of Sadie with a knife over her head, but the next moment she saw a flash of metal: Carter's Khopesh, it hit the demon right in the side.
Face of Horror is revealed to be one of Aphophis' minions and says he will seek his revenge on Sadie and Carter. Sadie gets Set into a white rope while his power is limited because she knows his secret name. Sadie throws the Feather of Truth into the sky to show what she sees to Carter and Set. Carter and Set see the serpent (Aphophis) as Sadie sees him. They form an alliance to defeat him.
Sadie and Carter make a deal with Set, Set can't come out of his place in the Duat until they call on him. If he doesn't comply Carter and Sadie can use Set's secret name against him. They let Set go into the Duat until they are ready to fight Aphophis.