At this point in the play, Macbeth has made his mind up to murder King Duncan, but before he does, he has to pay a visit to Banquo's bed chamber to ascertain whether or not he can trust Banquo after the murder.
As Banquo hears the foot-steps of Macbeth approaching his chambers, Banquo tells Fleance, his son, to
"Give me my sword."
This statement reveals that Banquo trusts no one, not even Macbeth. You must remember, that Banquo is a house guest of Macbeth's, and he should feel save, but his actions reveal that he does not.
After Banquo asks "Who's there?" Macbeth responds with an ironic "A friend"
At this point, Banquo recognizes that it is Macbeth, and he lowers his sword and they have a very interesting conversation. In this conversation, Banquo tells Macbeth that he dreamt of the witches, and Macbeth lies, and says that "I think not of them." Banquo's statement offers the opportunity that Macbeth needs to see if he can trust Banquo for he asks him
"Yet, when we can entreat an hour to serve,
We would spend it in some words upon that business,
If you would grant time."
Banquo responds by saying, "At your kind'st leisure."
Macbeth then tells Banquo that
"If you shall cleave to my consent, when 'tis,
It shall make honor for you.
In other words, if Banquo sticks with Macbeth, when the time comes, there will be something in it for him.
Banquo's response to Macbeth is
"So I lose none
In seeking to augment it, but still keep
My bosom franchised and allegiance clear,
I shall be counselled"
What Banquo says to Macbeth is he'll do whatever he says, as long as he can do it with a clear conscience and it has nothing to do with his allegiance to the king. Macbeth has just been given the answer to his question, and that is that he can not trust Banquo.
Thus in the beginning of Act II, it appears that Banquo doesn't trust anyone, not even Macbeth, and Macbeth most certainly cannot trust Banquo, but both men appear to respect each other, albeit with a pretentious respect.