When Rachel makes a promise to Sarah, it comes with a hefty price. Meanwhile, Helena and Gracie work with the Hendrixes, and Donnie takes Kellerman to task. Over at Castor, Coady and Benchman scheme to track down the Castor Original, and Rudy descends on DYAD for a much needed asset.

• Renée St. Cyr
• Graeme Manson
• John Fawcett

• Roger Cross
• Stephen McHattie
• Patton Oswalt