西德尼·布里斯托是大学生谁拥有一个不寻常的工作 - 她就是连她的朋友知道她做了什么秘密条件下为中央情报局工作的间谍。当男友提出悉尼告诉他，她做什么为生，她的雇主杀了他与程序一致。决定离开该机构，他们杀了她太多悉尼发现她实际上已经工作了SD6，一个机构，实际上是一个朦胧的犯罪组织世界性的了。悉尼加入中情局和作品作为一个双重间谍帮助中情局特工沃恩打倒SD6。她发现，她的父亲是在SD6和其他双重间谍的工作对一起。而跟随她的任务揭露预言Rambaldi人工的工作，她必须将信息反馈回CIA不吹她盖。

　　Sidney Bristow is a college student who has an unusual job – she is a spy working for the CIA under secret conditions where not even her friends knows what she does. When her boyfriend proposes Sydney tells him what she does for a living and her employers kill him in line with procedures. Deciding to leave the agency before they kill her too Sydney discovers that she has actually been working for SD6, an agency that is actually a shadowy criminal organisation world-wide. Sydney joins the CIA and works as a double agent to help CIA Agent Vaughn to bring down SD6. She finds that her father is the other double agent within SD6 and the pair work together. While following her missions to uncover the work of the prophetic Rambaldi she must feed information back to the CIA without blowing her cover.