First, I half-way did this to upset people. However, the more I think about it, the more it makes sense. So we know Bungie said Halo and Marathon are different universes. We also know about a certain ex-executive slipping and trying to recall his statement that MC and the security officer are the same people. These are givens, they are not refutable. Well here is how they are going to tie it in. It all has to do with 7, but you won't understand that unless you figure out the secret to 7 (think religion). So, here are a few things to tie it together. Slip space travel is actually travel between universes, and it is possible to exit into alternate opposed universes. That's my theory, but if you played all their games, you can see why I theorized on this, especially the third Marathon. We know the Halo distress takes place in the 2500's, irrefutable. We know outside of that the universe was relatively calm since the Forerunners, just skirmishes at the best between human colonies. We know in Marathon, the universes is in distress more often than not. We also know nothing of note happened in the 2500's. Bare with me, all this will tie in soon. We known Guilty Spark 343 recognized the Chief for some reason. Why, we don't know. We know at the end of Halo 3 the Chief's half of the ship split off from the other during a closure in slip space. So what does this all mean. For this to work we need to give a little way to science fiction. Let's assume that rogue AI, such as Cortana (Halo) and Beowulf (Marathon) are not confined to the physical limitations of dimensions like organic life and that information is open freely between them. Let's conclude that the Forerunner's were advanced enough to cross through time and dimensions. It's plausible considering them. In doing so they created an information link that transcends time and space for computers. Consider this could be very confusing to the AI involved. For this, I say Beowulf = Guilty Spark 343, in a manner of speaking. This is why he recognizes the chief. So when one universe is in distress, the other is calm. For every action there must be an equal and opposite reaction. When the Chief, Arbiter and Cortana tried to make the slip space jump, the ship split. Sending the Arbiter back to his universe and MC and Cortana to the Marathon universe. The Chief is put into stasis with the instructions to Cortana to wake him when he is needed. Cortana has a life span that is almost over. During their free float, Cortana overflows with information and implodes. The Chief is not monitored or awaken and passes in his perfect frozen state. One day he is found, genetically superior, with incredible technology. Someone, some scientist, decides he is a perfect test subject for a super soldier program. Graphs on cyborg technology onto his body to reanimate him. He is employed at what he does best war. Becoming employed to the security officer position for his extreme prowess on the battle field. Now we have a seamless transition that works with the Marathon time line and Halo time line. Bungie, I have a job, that I hate, so if you want to pay me to write story lines, let me know. I appreciate the ingenuity that you used to make sure when you left the death grip of MS that you could keep your hero for further games without violating IP ownership rights. Awesome job! And on the 7th day he rested.