Idris Elba: Heimdall
Heimdall : Tell me, Loki, how did you lead the Jotuns into Asgard?
Loki : Do you think the Bifrost is the only way in and out of this realm? There are passages between worlds to which even you, with all your gifts, are blind. But I have need of them no longer, now that I am king. And I say, for your act of treason, you are relieved of your duties as gatekeeper and no longer citizen of Asgard!
Heimdall : Then I need no longer obey you!
[draws his sword]
[Thor, Loki, Sif and the Warriors Three meet Heimdall]
Loki : Leave this to me. Gatekeeper, we seek...
Heimdall : You're not dressed warmly enough.
Loki : I'm sorry?
Heimdall : You think you can deceive me.
Loki : You must be mistaken...
Thor : Enough! Heimdall, may we pass?
Heimdall : NEVER has an enemy escaped my watch until this day. I want to know how it happened.
Thor : And tell no one where we have gone until we return. Understand?
Volstagg : [to Loki] What's the matter, silver tongue turned to lead?
Loki : What troubles you, gatekeeper?
Heimdall : I turned my gaze upon you in Jotunheim but could neither see you nor hear you. You were shrouded from me like the Frost Giants that had entered this realm.
Loki : Perhaps your senses have weakened after your many years of service.
Heimdall : Or perhaps someone has found a way to hide that which he does not wish me to see.
Loki : You have great power, Heimdall. Did Odin fear you?
Heimdall : No.
Loki : And why is that?
Heimdall : Because he is my king, and I am sworn to obey him.
Loki : He was your king. And you're sworn to obey me now. Yes?
Heimdall : Yes.
Loki : Then you'll open the Bifrost to no-one! Until I have repaired the damage that my brother has done!
Heimdall : You would defy the commands of Loki, our king? Break every oath you have taken as warriors, and commit treason to bring Thor back?
Sif : Yes.
Heimdall : Good.
[steps off the control platform]
Sif : So you will help us?
Heimdall : I am bound by honor to our king. I cannot open the bridge to you.
Fandral : Complicated fellow, isn't he?
Volstagg : Now what do we do?
[the Bifrost activates on its own]
Heimdall : Be warned, I shall uphold my sacred oath to protect this realm as its gatekeeper. If your return threatens the safety of Asgard, my gate will remain shut and you will be left to perish on the cold waste of Jotunheim.
Volstagg : Couldn't you just keep the bridge open for us?
Heimdall : Keeping the bridge open would unleash the full power of the Bifrost and destroy Jotunheim, with you on it.
Thor : I have no plans to die today.
Heimdall : None do.