SAM
‘Cause Alger Hiss just walked in with my secret pumpkin.
SAM
There’s a woman over there. I think she’s looking at me.
She is making a reference to William Manchester's book called "The Glory and the Dream". She calls the woman Alger Hiss who is one of the characters in that book. Hiss' secret documents and a microfilm were kept for many years in a hollowed out pumpkin. Ten years later the truth was revealed and those papers were used against Hiss in a purjury trial against him.
Cause Alger Hiss just walked in with my secret pumpkin.
I think Samantha thinks the woman that just walked in (she calls her Alger Hiss)has some incriminating evidence against her in, what she widely refers to...a pumpkin.