(71)It follows therefore that…
It followed therefore that any cyanide in the drink must have been put there by Anthony Marston himself.

「It follows therefore that…」は「それゆえ・・・ということになる」の意。

(72)put things straight / lock up / turn in
“No, sir. I’ll just put things straight in the dining room and make sure everything’s locked up right, and then I’ll turn in.”

「put things straight」は「きちんとする」の意。「lock up」は「かぎをかける」。「turn in」は「go to bed」。

(73)fall in
The shrunken lips fell in.

「fall in」は「内側へくずれる」。

(74)cook one’s goose
He’d cooked Seton’s goose all right!

「cook one’s goose」は「・・・を破滅させる」。

(75)withdraw into oneself
He’d avoided people after that - withdrawn into himself.

「withdraw into oneself」は「自分の殻に引き籠る」。