Chuck finds a bug in the Buy More, which leads Casey and Sarah to take drastic measures to find out whether the truth about Chuck has been discovered. Whilst facing the possibility that he may have to leave his life forever, Chuck loses something very important- the engagement ring for Ellie entrusted to him by Captain Awesome.

The episode begins with a flashback to the year 2004, where John Casey is involved with a female Russian named Ilsa, who claims she is a photo journalist. Later, in present day, Ilsa returns with a fiancé, named Victor Federov. Things get complicated when it is revealed that Ilsa is a French spy.