In the fourth season (1966–67) "Doctor Who" story "The Power of the Daleks", second incarnation of the Doctor, played by Patrick Troughton, awakens from his first regeneration and eventually faces one of his old nemeses, the Daleks. Human space colonists examine "dead" Daleks and, upon their re-activation, conjecture as to "what sort of positronic brain must this device possess". However, the Daleks are actually organic life-forms that were encased in robotic shells, and thus do not possess the purported positronic brain and, in any case, do not obey the Three Laws of Robotics.