[[WMG: The reason [[spoiler:Kai can't find Erica in 2019 is because she's a therapist at that point.]]]]
Thus [[spoiler: she no longer exists in the 'real' world in the sense of having an identity that he can actually find.]]
** More than likely [[spoiler: confirmed]] by 3x12, "Erica, Interrupted".
*** Sort of [[spoiler:Jossed]] by Episode 4x08, "Please, Please Tell Me Now". [[spoiler:Dr. Fred tells Erica that she really is dead in 2019, following a subway bombing that kills her and many others. But then Erica receives a visit from her future self, and learns that there are alternate realities. Erica's life seems to diverge into two branches upon the losing of her virginity: one timeline is where she is still alive in 2019; the other is where she is dead. Unfortunately, the reality where Kai is from is the one where she's killed in the bombing.]]

[[WMG: Doctor Tom is [[Series/DoctorWho The Doctor]].]]
And I didn't even say "X is a time lord" ... ("facepalm")
Just think about it. He is a DOCTOR!
He travels through TIME AND SPACE!
His office is BIGGER ON THE INSIDE! (my theory is that his office IS the doorways that Erica walks through)
* He also carries a water pistol (Episode 3x01, "The Rabbit Hole), [[Recap/DoctorWhoS30E2TheFiresOfPompeii just like Ten]].
* Alternatively, the Doctor was the original therapist.
* One of the doors in the group therapy room certainly looks like it's got roundels on it...

[[WMG: Erica's voice overs are things she's saying to other people when she's a therapist.]]
The voice overs seem to speak in an older more experienced fashion and almost in a more teaching fashion as if she's telling people things.

[[WMG: Doctor Tom's daughter Sarah is a [[Series/OrphanBlack Project Leda clone]]]]

This may also account for why it was so difficult for Dr. Tom to find her: either Sarah Manning accidentally erased Sarah Wexler's records while trying to conceal herself from a con gone wrong, or Dyad abducted her to do more in-depth studies on her after she ran away.