1. This Half Life 2: Episode One walkthrough is played on normal difficulty on the Xbox 360. Watch the introductory montage to be berated by Dr. Breen, discover that the Vortigaunts rescued Alyx, then see them taunting G-Man.
2. After being rescued by Dog, you are brought to a very relieved Alyx. Receive the Gravity Gun from Dog.
3. Alyx climbs onto this ledge, displaying an athleticism that apparently you lack. You'll need to solve your first puzzle to get up there and rejoin Alyx and Dog.
4. This should be pretty obvious to Half Life 2 veterans -- use the left trigger to grab these boards with the Gravity Gun.
5. This metal ramp will then drop down, allowing you to cross to the area above.
6. Grab the two medkits on this table then learn from Drs. Vance and Kleiner that you'll need to re-enter the Citadel and shut down the core.
7. Crouch to slip beneath the debris that Dog lifts for you.
8. Drop off the ledge to begin another of Half Life's infamous jumping puzzles.
9. Crouch to slip beneath this debris, then press A to jump across the short gap in the ledge beyond.
10. Your Gravity Gun removes this wrecked car blocking the path.
11. Next, you need to enter the Citadel through that opening ahead. But how to get across the chasm?
12. Dog comes up with an idea. (Apparently he's smart as well as adorable.) He fetches this vehicle which he wants throw into the Citadel - with you and Alyx inside.
13. Press X to enter the van on the passenger side then sit back as Dog successfully throws you clear of the chasm and into the Citadel.
14. Once across, stay put for another brief thrill ride as the van slips farther into the Citadel. Press X to exit the van once it finally comes to a stop.
15. Watch the van tumble over the ledge then continue down the corridor to Alyx's right.
16. Jump over this railing to the floor below; Alyx follows.
17. Through a short corridor you'll come to this area. Stalkers prevent Alyx from lowering the force field.
18. She is, however, able to disable this nearby force field. Note the Roller Mines ahead; Alyx has a plan.
19. Crouch to pass through this crawlspace beyond the deactivated force field.
20. Drop to this ledge then take a big leap to the indicated lift. You'll take damage but don't worry -- there's a health/suit energy combo station just ahead.
21. The lift begins moving up and down. Exit when it's in the down position then heal at this combo station. Approach the red button ahead/left -- pressing the button will release the roller mines in the tube above.
22. Use your Gravity Gun to deflect all the mines but one.
23. Return to the lift, carrying one of the roller mines.
24. Ride the lift back up to Alyx. Hold the mine still while she reprograms it.
25. Drop the mine; it will slip behind the force field and kill the two Stalkers, allowing Alyx to disable the force field.
26. Pass through the previously-inaccessible room then continue to this ledge where you'll see several soldiers meet a firey end. Continue left and crouch under some debris.
27. Ascend the stairs and cross a bridge before using your Gravity Gun to clear the path of this debris.
28. Up a short flight of stairs is this railing. Hop over to the ledge below.
29. Follow the ledge to this energy bridge. Soldiers try to cross but are swept away by a vortex.
30. To cross the bridge safely, wait for the vortex to subside then sprint across by pressing the left bumper as you run.
31. Alyx crosses the bridge after you. Is that the look of love or what?
32. Follow the corridor then hop over another railing to this room with a glass floor.
33. Watch as the console switches from a recording of Dr. Breen to an image of an even creepier insect. The giant bug slides underneath the floor then emerges upright across the room.
34. The bug vanishes in a pulsating flash. Follow Alyx to the nearby exit and she'll deactivate the force field.
35. Traverse the corridor a short distance then become temporarily trapped in this room. Your Gravity Gun is stripped from you, then is supercharged into a more powerful version, able to pick up heavier objects and even living persons.
36. Follow along to this half-charged energy bridge. Note that the half that is charged coincides with a lighted socket, lower/right. The unlit socket lower/left can be charged by tossing one of these energy balls into it, thus activating the bridge.
37. Cross the bridge and be met by soldiers -- time to show them that newly-supercharged Gravity Gun. Grabbing them with the left trigger is preferred at distance, while a close-up solider is easily dispatched with a jolt from your right-trigger fire.
38. Next up is this completely-unpowered bridge. Shoot energy balls into both sockets to activate the bridge, then cross to battle more soldiers and Overwatch.
39. This next bridge is a bit tricky; you'll need to bank an energy ball off the wall to get it past the clear shield blocking the left socket.
40. Cross the bridge then duck under this debris. Battle Overwatch on the other side.
41. Follow the corridor to this ledge and hop over the gap to continue.
42. Witness these styders as you cross the glass bridge. A gunship follows, then crashes.
43. Follow the ledge to this door then pass through after Alyx opens it.
44. The corridor leads to this combo station. Grab an energy ball from the beam off-screen to the left.
45. Walk to the end of the ledge and throw the energy ball into this socket. The lift descends.
46. Look up. Debris falls periodically. You can either step aside, grab it with your Gravity Gun's left trigger, or shoot it with the right trigger.
47. The lift stops. Use your Gravity Gun to pull the pink console off the wall. You can then shoot an energy ball through the opening; it will bounce off the wall and into the socket if you aim just right.
48. The lift resumes and so does the debris, including this large piece of something. I found it best to grab it with the Gravity Gun's left trigger, then toss it aside.
49. Activating this socket only works briefly as a Stalker reverses the lift. Take him out with a well-placed energy ball then re-energize the socket to send the lift on its way for good.
50. Quickly exit the lift once it arrives to avoid this final chunk of debris.
51. Fill up on health and energy at this combo station then continue ahead to load the next level.