The wine was drugged.

He had watched the decline of Dyck's fortunes with an eye of appreciation; he had seen the clouds of poverty and anxiety closing in.

He had known of old Miles Calhoun's financial difficulties.

He had observed Dyck's wayside loitering with revolutionists, and he had taken it with too much seriousness.

He knew the condition of Dyck's purse.
He was not prepared for Dyck's indignant outburst.
"I tell you this, Erris Boyne, there's none has ever tried me as you have done! What do you think I am--a thing of the dirty street-corner, something to be swept up and cast into the furnace of treason?
Look you, after to-day you and I will never break bread or drink wine together.
No--by Heaven, no! I don't know whether you've told me the truth or not, but I think you have.