Half Life 2 Episode One

In chapter two of the game, "Intervention", when you go up the ladder to the first floor, and after you get done opening the first machanism that shoots a beam at the Core, and then the door opens. Now inside at the end of the hall there is a cover that when uncovered exposes you to some energy balls. And in that hallway there is a blocked door, and you cant do anything else. My question is, what did i miss, and where do i go next to advance the story, ive tried looking up walkthroughs, but they lead nowhere. Ive even tried updating the game, and i still get nothing. Ive only updated to UPDATE 1 of the game, because i dont think there are anymore updates for Episode One, right? Well I want to finish the game, but how am i supposed to when i cant do anything else. AAAAAAAAAAHH