Vandamm (James Mason)’s Timeline and Summary

Vandamm pretends to be Lester Townsend after taking over the Townsend mansion. He tells Thornhill he knows he's George Kaplan and threatens to kill him if he doesn't reveal everything he knows.
Vandamm has the woman who has pretended to be "Mrs. Townsend" (we later learn she's Vandamm's own sister) give another "performance" to cover up for the baddies who've taken over the Townsend estate.
Vandamm sends one of his henchman to kill the real Lester Townsend in the UN.
On the train headed for Chicago, Vandamm receives a note from Eve Kendall, asking for advice about what to do with Thornhill.
Vandamm tries to have Thornhill killed by a souped-up crop-duster plane.
At an auction in Chicago, Vandamm buys a pre-Columbian statuette; it turns out the figurine's filled with microfilm, used by Vandamm's spy ring to smuggle government secrets out of the US.
Vandamm starts to suspect that Eve Kendall's working for someone else, since she's been acting strange and telling lies for Thornhill.
When Eve shoots Thornhill, he believes that she's on his side again.
But then Vandamm learns from Leonard about Eve's betrayal. He plans to kill her by throwing her from a plane.
As Leonard and others chase Eve and Thornhill all over Mount Rushmore, Vandamm's captured by the Professor and police.