Yin and Yang prepare to go on vacation. Coop returns and tries to warn them of The Night Master's energy escaping, but they ignore him until it's too late. / Coop's mom is throwing a "welcome back/thanks for saving the world all by yourself" party, and Yin and Yang are the only ones not invited. Meanwhile, three flunkies join together and try to get into The Night Master's fortress. However, they need the spare key, which the Night Master gave to Coop!