The Overlooker is the Hierarchy official in Tinker, Tenor, Doctor, Spy who commands the surveillance ship watching Voyager and plans a raid based on the Doctor's daydreams.
The Overlooker appears in the sixth-season Voyager episode Tinker, Tenor, Doctor, Spy. He supervises a vessel of the Hierarchy, a rigidly bureaucratic species that observes passing ships from hiding and attacks only when its leadership calculates an acceptable return.
One of his subordinates, Phlox, taps into the Doctor's perceptions as a way of gathering intelligence, not realising that what he is seeing are fantasies in which the hologram commands the ship. The Overlooker submits a plan built on this faulty picture.
Phlox, fearing punishment, secretly warns the Doctor. When the attack comes the Doctor poses as the Emergency Command Hologram and threatens to fire an invented photonic cannon, and the Overlooker, confronted by exactly what his data predicted, withdraws.