intervene

intransitive verb | \ ˌin-tər-ˈvēn \ | in·ter·vene
  1. : to occur, fall, or come between points of time or events may be held liable even though other independent agencies intervene between his negligence and the ultimate result —Hooks Superx, Inc. v. McLaughlin, 642 N.E.2d 514 (1994)

  1. a : to come in or between by way of hindrance or modification intervene to stop a fight

    b : to become a party to a legal proceeding begun by others in order to protect an alleged interest in the subject matter of the proceeding the Commissioner of Internal Revenue was granted leave to intervene —P. A. Freund — compare implead, interplead, join