ANALYZE THE EXAMPLE TEXT (VERBAL IRONY)
Example:

Hathorne: But a poppet will keep fifteen years, will it not?
Proctor: It will keep if it is kept, but Mary Warren swears she never saw no poppets in my
house, nor anyone else.
Parris: Why could there not have been poppets hid where no one ever saw them?
Proctor: [furious] There might also be a dragon with ve legs in my house, but no one has
ever seen it.
Parris: We are here, Your Honor, precisely to discover what no one has ever seen.
Proctor: Mr. Danforth, what profit this girl to turn herself about? What may Mary Warren
gain but hard questioning and worse?
Danforth: You are charging Abigail Williams with a marvellous cool plot to murder. Do you
understand that?

Verbal irony is used when the speaker means the exact opposite of what he says. In the text above, the charge which was laid on Abigail was a plot to murder. Danforth, who was clearly frustrated, described it as "a marvelous cool plot".

Apparently, he means the exact opposite of what he said because the charge was in no way marvelous nor cool. It was a grievous offence.

Answer Link