𝗙𝗜𝗢𝗡𝗔 𝗙𝗥𝗢𝗦𝗧:Fiona Frost (フィオナ・フロスト, Fiona Furosuto?) is a major recurring character of the SPY x FAMILY series. She is a spy for WISE who acts under the codename "Nightfall" (〈夜帷とばり〉, <Tobari>?). She works undercover as an assistant to Loid Forger at Berlint General Hospital to provide him with mission details.