 The Chief , Arbiter and Guilty Spark discover that the Ark is constructing another Halo to replace the one that the Chief previously destroyed . The Chief decides to activate this Halo ; the ringworld would eliminate the Flood infestation on the Ark while sparing the galaxy at large from destruction . To activate the ring , the Chief rescues Cortana , who has the Activation Index of the destroyed Halo , from High Charity and destroys the city . Arriving on the new Halo , Cortana warns that Gravemind is trying to rebuild itself on the ring . The Chief , Arbiter , and Johnson travel to Halo 's control room to activate the ring . Guilty Spark explains that because the ring is not yet complete , a premature activation will destroy it and the Ark . When Johnson ignores his warning , Guilty Spark fatally wounds him to protect " his " ring . Although the Chief destroys Guilty Spark , Johnson soon dies of his injuries . Chief activates the ring , and escapes the ring 's self @-@ destruction on the UNSC frigate Forward Unto Dawn . However , the force of Halo 's blast causes the slipspace portal to collapse , resulting in only the front half of Forward Unto Dawn , carrying the Arbiter , making it back to Earth . 
