it may be observed that in this part of the story the earliest version had a strength that was diminished later , in that the duration of tinuviel 's imprisonment and her journey to beren 's rescue relates readily enough to that of beren 's captivity , which was intended by his captors to be unending ; whereas in the later story there is a great deal of event and movement ( with the addition of luthien 's captivity in nargothrond ) to be fitted into the time when beren was awaiting his death in the dungeon of the necromancer .