Elizabeth Henstridge, who acted in J.J. Abrams and Mark Schwahn’s Shelter pilot, will play the science-savvy Agent Gemma Simmons in the pilot for Joss Whedon’s S.H.I.E.L.D. TV series.  She will join the previous announced Clark Gregg (Agent Coulson) and Ming-Na (Agent Melinda May--see "Ming-Na Cast in 'S.H.I.E.L.D.'") as well as Iain De Caestecker, who will play the technology whiz Agent Leo Fitz, who will often be at loggerheads with Henstridge’s Agent Simmons.  De Caestecker has played the lead in two very well received BBC series, The Fades and Young James Herriot.
According to The Hollywood Reporter, which broke the news of the addition of Henstridge and De Caestecker to the pilot, Joss Whedon is slated to write the S.H.I.E.L.D. pilot along with his brother Jed and Maurissa Tancharoen, and he “will direct the pilot if his schedule permits.”