A Dance of Chance.

Reid does not sleep because when he does, he sees Maeve in his dreams. He has been in a downward spiral since her death.

At the end of the episode, Reid finally falls asleep after solving a case. He dreams of her yet again.

They are in a library. She teases him. Tender glances are exchanged before Maeve rises and stretches her hand towards him.

Maeve: Dance with me.
Reid: Why?
Maeve: I want to hold you once before I'm a ghost of a memory.

~ Criminal Minds
Season 8, Episode 20
Alchemy