The Flash, Season 4

Harry:
You're the team leader. Team leader's supposed to make the tough call.

Iris:
I made a call. I said we would look for both of them (Barry and Caitlin).

Harry:
No. Looking for both of them is not a choice. We're overtaxing our resources, our people, because you won't face the hard truth. And the hard truth is, we can't look for both. We can only look for one.

Iris:
Harry, I just made a vow to love and protect Barry. To stand by him through thick and thin. And now you're asking me to choose between my husband's life and me friend's? [Harry nods] I can't. I, I can't do that–

Harry:
You have to. Or you risk losing them both. You have to choose.