Mulder and Scully investigate some deaths during the Season 4 cancer arc, post Elegy and pre-Demons.
This is one of my favourite authors and stories. It hits the ground running, and keeps up the pace through the whole marathon.
Just as a sidenote, if you're undergoing chemotherapy, please seek your doctor's advice regarding the use of condoms before you and your partner do the wild thing in the morgue. 😉