Dr. Gero's Androids #13, #14, and #15 are awakened by the laboratory computers and immediately head to the mall where Goku is shopping. After Goku, Trunks, and Vegeta defeat #14 and #15, #13 absorbs their inner computers and becomes a super being greater than the original three separately were. Now it is up to Goku to stop him. 

(Source: ANN)