"The children of Skaro must walk again!" - Dalek Sec
After the Cult of Skaro escaped from the Battle of Canary Wharf using emergency Temporal shift they arrived in Manhatten: New York in the 1930's and began to try and create new Daleks.
Their leader Dalek Sec decided that unless the Dalek's evolve they will become extinct. The Cult begins to kidnap humans, smart ones become part of the Final experiment while the less intelligent humans become Pig slaves and are used to capture more humans.
Dalek Sec plans to mix the bodies of humans with Dalek DNA which will create a new race of Daleks. After many humans are kidnapped, Sec decides that a final experiment should be completed.
This "Final Experiment" involved Mr Diagoras, head of constructing the Empire State Building and the human selected as most Dalek-like, being merged with the body of Dalek Sec, leader of the Cult, inside the Dalek Supreme's casing. The experiment was to allow the Daleks to have a new life and to recreate the Dalek Empire.
Although the other three Daleks of the cult of Skaro disagree with Sec, Sec argues that their quest to remain pure has led them to their near extinction. Sec merges with Diagoras and becomes the first Human Dalek.In his new body, Sec feels humanity and eventually with help from the Tenth Doctor, decides to make the new Human Daleks less Dalek and more human. Even deciding that Davros creator of the Daleks was wrong.
Later, the Daleks, under command of the human-Dalek, set to work combining the bodies of several hundred humans who had been placed into stasis with a mixture of Dalek and human DNA, in an attempt to combine the Dalek and human Factors. However, the still-cyborg Daleks sabotaged the project, causing fully-Dalek DNA to enter the minds of the humans, instead of the hybrid forms. However, the Tenth Doctor sabotaged this work by attempting to destroy the transmitter at the top of the Empire State Building, and when this failed clung to the transmitter as a solar flare lightning strike hit the transmitter, causing the Doctor's Gallifreyan DNA coding to be mixed with the Daleks', causing Dalek-human-Time Lords who disobeyed the Daleks' orders and destroyed Daleks Thay and Jast.
Furious at their failure, Dalek Cann the last Dalek uses a high pitch sound to destroy all the Human Dalek Time Lords.