Cassie Bowden (Kaley Cuoco) is a sober Los Angeles resident who moonlights as a CIA asset in her leisure time. However, when she is unwittingly witnessing a murder while on assignment abroad, she finds caught in yet another international mystery. Los Angeles, Berlin, and Reykjavik were used to film the season.
Returning series regulars Cuoco, Zosia Mamet, Griffin Matthews, Deniz Akdeniz and Rosie Perez. Returning recurring guest stars T.R. Knight, Yasha Jackson and Audrey Grace Marshall. The season also stars new series regulars Mo McRae, Callie Hernandez and JJ Soria, as well as new recurring guest stars Alanna Ubach, Cheryl Hines, Jessie Ennis, Mae Martin, Margaret Cho, Santiago Cabrera, Sharon Stone and Shohreh Aghdashloo.