It was simmering away, lurking in the murky depths of his conscious, patiently waiting for the perfect moment to rise to the surface. Spencer never thought the time would come, that perfect moment that part of him had been waiting for. But he was sorely mistaken. And it came in the form of you, [Y/N] [L/N]. The new agent of the Behavioral Analysis Unit, his co worker, his peer. But above all else, you were his catalyst. [Eventual!UnSub!Spencer x BAU!Reader]