In this scene from Fringe, the team finds two sets of DNA in the specimen taken from a crime scene.
Check out the official promo for Stowaway here. The team looks into a killer that attaches herself to suicide victims on the installment.

Fringe Season 3 Episode 17 Quotes

William Bell: Now, Olivia's brain can accommodate my consciousness for several weeks, before would anything happen to her.
Peter: Weeks? Not a chance.
William Bell: And, I am confident Walter will find a more stable home, long before that.

I understand that this could take some time getting used to. Imagine how I feel, I never knew that a bra was so binding.

William Bell