This is a walkthrough on the 6th episode. It is fit for any difficulty but as I play Legendary this guide is specially suited for players as such.
Escape Plan:
Enemies include: All covenant infantry excluding hunters, phantom dropships, and Crawler Infantry & Primes.
Vehicles include: Ghosts, phantoms, and shade turrets.
NOTE: YOU CANNOT CHOOSE A LOADOUT ON THIS CHAPTER. IT IS NOT A GLITCH.
This episode starts off with your spartan chained to the wall in a covenant-controlled prison. Thanks to an airstrike by Miller you free yourself and stab the Zealot guarding you in the back, and take his Covenant Carbine. You also grab his plasma pistol. You have to fight through covenant forces after being freed, which include several grunts, jackals, and elites. You can find ghosts in this area; use this to your advantage. Stun enemy ghosts with your plasma pistol. Eventually you will need to unlock a door leading you into the next area.
After doing so, a large amount of suicide grunts will rush you. Take them out quickly. Proceed into the next area (easier if you have a ghost). Kill all hostiles in the area, and make sure to focus fire on the shades as they do extra damage. After enough carnage, Roland tells you it might be possible to jack a Covenant phantom. You should eventually unlock another door which leads into a stairwell that contains jackals and elites. After burning through the small staircase, you've reached the phantom loading docks.
Now, you need to kill a small amount of covenant until you get a message about Icebreaker squad. You need to break into this room and free them. First however, you will meet Covenant resistance including most types of enemies. After clearing them out their Crawler buddies start spawning and will bombard you with Suppressor and Boltshot fire. Use the cover provided and kill them slowly, while keeping yourself safe. After clearing out the crawlers you can free Icebreaker squad, where you meet the country-accent Lt. Murphy (he plays a major role in transportation). Along with him are 4 other marines. Sadly, though, they die quickly and aren't of much use due to the fact that their only weapons are plasma pistols.
In the climax of this chapter Lt. Murphy will start to mess with Covenant technology to get the Phantom under control of UNSC forces. You will have to defend Murphy from several waves of covie attackers, although thankfully they don't seem to go after him (for those of you who die on legendary often, this gives you more of a chance). After completing the objectives, hitch a ride and high tail it from that prison. Crimson is free.