Castiel turns up at the bunker one day. With a sleeping girl. Turning to Sam he tells him this is deans soulmate. And she is being targeted by the angels and demons in a way to bribe Dean to do their dirty work. Keeping the secret from Dean is a job in itself. But what happens when Dean learns he gets along with her. More than friends.
Falling asleep one night as usual. Nothing special about it. But you open your eyes to match a pair of violet ones staring back at you. Considering whether or not you are a threat.