Snape's half truths in "Spinner's End"/why take the vow

[Tonks]

No: HPFGUIDX 149489

Narcissa loves her son.  Snape is a both a family friend and a very 
powerful wizard with influence in both camps. It is logical that she 
would go to him, as we all would if we needed a favor and our friend 
was a person with access to the most powerful people.  Snape is also 
Draco's teacher so he is in the logical position to look after Draco 
since Draco will be in school most of the year. 

Narcissa trust Snape to care about her, her child and his old friend 
Lucius.  Are all DE just cold hearted, all for themselves, villains 
like LV?  I think the answer is, No.  They are more human that LV.  
They love and care for their families just like everyone else.	 One 
might wonder why a person would become a DE, but that is another 
post.

Narcissa is upset and when she "began to cry in earnest, gazing 
beseechingly all the while at Snape", Snape must have been looking 
into her eyes.  She then goes on to think about the task that Draco 
has been assigned saying "it's too dangerous! This is vengeance for 
Lucius's mistake, I know it!"  

Then Snape looks away. We are led to believe that he looks away 
because he can not bare to see her tears.  That might be part of it, 
but I think that until that moment he did not know what Draco's task 
was.  It was in that moment when he saw it in her mind that he was 
on the verge of dropping his guard and showing his own thoughts.  It 
was this reason that he turned away.  He stayed turned away for a 
few minutes, while he was composing himself.  He is still turned 
away when he says to her "If Draco successes he will be honored 
above all others".  I think he is still turned away from her so that 
the shock does not show in his eyes.  But clearly this is the first 
time that he knows what the task is.

Why would Snape need to take so long to compose himself? Why might 
there be shock in his eyes?  Maybe because LV told him this "I have 
a little task for Draco, being a child he may not be up to it, and 
so if he can't succeed in doing it I will expect you to do it for 
him".  At the time Snape probably thought "no problem, simple task a 
kid could do, not to worry."  LV, being the type that he is, would 
not have told Snape the whole story.  Snape only realizes the 
position that he is placed in when he see the task in Narcissa's 
eyes.  (He must be thinking "oh s---!")

It is a small leap from this to Snape's taking the vow.  He did not 
know that Narcissa would ask the third provision of the vow.  He is 
damned either way anyway. So he goes on with the third provision in 
order to protect his cover, now fully realizing the terrible place 
in which he has been placed, not only by the vow, but by LV.  And we 
see his hand shake.  

Poor, poor Snape.  `Oh what a tangled web we weave when first we 
practice to deceive.'  It came back to bite him.  Spinners end 
indeed!

Tonks_op