Angel Investigations is the name of a detective agency run by the title character Angel on the WB television series Angel (a spin-off from Buffy the Vampire Slayer). It is sometimes abbreviated as AI. The agency allows Angel to openly advertise his willingness to assist people in trouble without specifying the agency's specialization in supernatural cases; their slogan We Help the Helpless is especially appealing to people who are unfamiliar with the supernatural world and therefore are afraid to ask for help, fearing they will be considered crazy, but who are nonetheless in desperate need of aid.
Throughout most of the series' run, the agency has employed most of the characters, and provided the series with a steady income of storylines. Because of this, AI is somewhat synonymous to the group of main characters. It is also known as Team Angel, a term that could be employed even following the demise of Angel Investigations as a business. Angel Investigations on Wikipedia