Now we will proceed.

When Mr.Brenton sat down to that dinner he was perfectly well.

When he arose from that dinner he was feeling ill.

He goes to bed.
He sees no one but his wife after he has left the dinner-table, and he takes nothing between the time he leaves the dinner-table and the moment he becomes unconscious.

Now, that poison must have been administered to Mr.Brenton at the dinner-table.