Alan Blackblade

Alan Blackblade is a member of the Thieves' Guild who appears in Chapter Seven. He can be found standing in the street, in the shadows of the house located across the street from Gantolandan's Home in the district of Southeast Baldur's Gate.
Speaking to him will provide you with useful information as to what Sarevok is up to and it will result in a quest entry under the title "The Rise of Sarevok".