 In "Buried Secrets," the Turtles discovered a Kraang ship beneath April's family farmhouse, where her great-grandfather supposedly discovered it and the Kraang inside, leading to generations of experimentation on the deceased relatives on April's mother's side of the O'Neil family until culminating in experiments they performed on her mother.They also discovered a clone of April's mother who was sealed in the ship due to being unstable, and managed to defeat her.In "Return to New York," the Turtles returned to find the city under the control of the Kraang, with all but a handful of humans-including the Earth Protection Force-being either mutated or fitted with mind control devices.