Simplify the following text for a Grade 9 native English-speaking person.
Original: The episode depicts a Dalek invasion of Earth led by Caan , Davros , and a red Supreme Dalek , who has kept Caan and Davros imprisoned in `` The Vault '' , a section of the Dalek flagship , the Crucible .
Simplified: The new Dalek army was led by a Supreme Dalek , who kept Davros imprisoned in a `` Vault '' ; Davros said that he and the Supreme Dalek had reached `` an arrangement '' .