Read this strip at gocomics.com.
This strip is a reprise of the joke from
Sunday, 2/15/53. In that earlier strip, Lucy doesn't seem quite so vicious, because in that one Linus is trying to play with her stuff, while here, Lucy is outright taking Linus's cookie unprovoked.
This might mark the first moment where Lucy seems to be truly evil, in a way it's impossible to explain with another motive.
I love Linus's face in the second panel.