Did Barrigan know Sullivan was a mole before Sullivan’s arrest on the rooftop?
Or did Barrigan put the pieces together when Brown most likely asked him to back him up after Costigan called him to support his arresting of Sullivan.
shareI’m thinking he knew. Costello probably had Barrigan keep an eye on Sullivan to ensure he was staying loyal. It seemed the higher up in rank Sullivan got the less Costello trusted him.
shareThat sounds right.
shareBarrigan saying, "Did you think you were the only one he had on the inside?" seems to indicate he knew Sullivan was a mole - as you say, keeping tabs on him. But not vice versa/ Costello did indicate he was concerned Sullivan might be succumbing to his desire to be respectable but reminded him who was boss. And as Billy taunted Sullivan, Costello trusted him more than he did his mole.
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