The word of a snail on the plate of a leaf?
It is not mine. Do not accept it.
Acetic acid in a sealed tin?
Do not accept it. It is not genuine.
A ring of gold with the sun in it?
Lies. Lies and a grief.
Frost on a leaf, the immaculate
Cauldron, talking and crackling
All to itself on top of each
Marriage, while seemingly hopeful, soon becomes deceitful. 
 Note the anger expressed in the repetition of ‘lies’. The one word sentence gives it emphasis. It is interesting that Plath writes ‘a grief’ — the indefinite article is included. Perhaps this is to give it emphasis. Or else it may imply that this is only one of many griefs.
The Couriers