A failure in planning is a plan for failure.
In the middle of a routine shopping trip on Coruscant, C-3PO is abducted by the bounty hunter Cad Bane. Bane is looking for information about the Senate Building on behalf of Jabba the Hutt. Finding C-3PO devoid of useful information, Bane and his accomplices kidnap R2-D2 and extract the vital data, before memory wiping the droids of the incident, and letting them on their way. The floor-plans and security details of the Senate building are part of a plot engineered by the Hutt families to free their imprisoned brother, Ziro the Hutt, who holds potentially damaging information about Hutt activities.