In which we get reacquainted

 My table's on its third campaign dating back to the Before Times.  SO hasn't played since previous campaign so while she knows the players her PC doesn't know THESE PCs.  And she's decided she'd like to take her place at the table again.  Good so far.

Party is in the middle of a dungeon.  We ended prior session having found a secret door.  What might be behind it?  Last night we began by opening the door.  A 15' diameter circular room.  In the center is a large opalescent bubble.  Visible inside is what appears to be the stature of a female spell caster, mid-spell.  After taking 2-3 minutes to THOROUGHLY examine the room the party notices that the statues hair is wafting VERY slightly, as a small bead of perspiration makes its way from her scalp down the side of her face.

Upon discovering this the party exit the room and use Mage Hand to manipulate the bubble into bursting.  The "statue" spring to life shouting "I'm here to help.  Have you found both keys?"  Kim was in the next room and I cued her to come in and sit down and away we went.  Turns out she was "rescued" at the conclusion of the prior campaign and placed here in temporal stasis to help the party.  

"New" character introduced mid-adventure.  A few story elements/hook planted with her.  Instantly accepted as helpful based on the info she exposited.