Marvel and ABC have unveiled the official episode description for the upcoming season 2 premiere of Agents of S.H.I.E.L.D., which reveals that Hayley Atwell’s Peggy Carter will be making a guest appearance ahead of headlining her own Captain America spin-off show Agent Carter later this year. Also set for guest appearances in ‘Shadows’ are the returning B.J. Britt (Agent Triplett), Adrian Pasdar (Glenn Talbot) and Patton Oswalt (Agent Koenig); check out the full synopsis here…

“Shadows” – Coulson and his team are now wanted fugitives with limited resources–but that’s not stopping them from keeping the world safe from powerful and unseen threats everywhere. However, with new members they hardly know, will S.H.I.E.L.D. ever be trusted again? Watch “Marvel’s Agents of S.H.I.E.L.D.,” on the ABC Television Network.

Guest starring are B.J. Britt as Agent Antoine Triplett, Nick Blood as Agent Lance Hunter, Adrian Pasdar as Brigadier General Glenn Talbot, Henry Simmons as Alphonso “Mack” Mackenzie, Patton Oswalt as Agent Billy Koenig, Lucy Lawless as Isabelle “Izzy” Hartley, Wilmer Calderon as Idaho, Reed Diamond as Daniel Whitehall, Hayley Atwell as Peggy Carter, Brian Patrick Wade as Carl Creel, Matthew Glave as Roger Browning, Simon Kassianides as Sunil Bakshi, George Stephanopoulos as self, Raquel Gardner as Carla Talbot, Ben Turner Nixon as Hydra Officer, Franco Vega as Military Leader, Rich Ceraulo as Soldier #1, and JB Tadena as Private Tilden.

So, is this going to be a flashback to the early days of S.H.I.E.L.D., or might we see another appearance from Old Peggy?

Agents of S.H.I.E.L.D. returns on September 23rd with Clark Gregg (Phil Coulson), Ming-Na Wen (Melinda May), Chloe Bennet (Skye), Iain De Caestecker (Leo Fitz), Elizabeth Henstridge (Jemma Simmons) and Brett Dalton (Grant Ward) all returning as regulars.