Paul, who is apparently in prison (probably in either Rome or Ephesus), writes to a fellow-Christian Philemon and two of his associates. Paul writes on behalf of Philemon's slave, Onesimus. Beyond that, it is not self-evident as to what has transpired. Onesimus is described as having been 'separated' from Philemon, once having been 'useless' to him (a pun on Onesimus' name, which means 'useful'), and having done him wrong. (Wikipedia)