Lost & Bound is the episode right before Charmed & Dangerous and it sets up plots that ultimately are ignored the very next episode and remainder of the season.
We learn about Firestarters and how The Source abducts these witches to add them to his personal guard. Come the very next episode....no Firestarters or anything of the sort to be found.
Phoebe has an entire arc about not wanting to lose herself with her marriage to Cole. After C&D she literally loses herself to being Mrs.Cole Turner.
Cole is attempting to acclimate to human life. Gets a job with Paige and has what seems to be a promising future role in the show. He becomes The Source at the end of C&D and his entire human arc is thrown away.
By - primal_slayer