Resorting to Danger!
In 2009, Nick asks Nancy to come to the Redondo and pose as the new general assistant in order to investigate why bombs are going off. Nancy eventually finds out that he is embezzling money from the clients and the Redondo by overcharging and keeping some money for himself.
In the event that Nick is the bomber, he was using the bombs to divert attention from him and postpone the audit of the next month. The "construction accidents" also made the guests want to pay extra to get into the Redondo.