This article contains plot spoilers for the 2017 series of Twin Peaks.
Anthony "Tony" Sinclair was an insurance agent at Lucky 7 Insurance.
He later stood in Dougie's office, trying to get him to speak until Sinclair left when police arrived to speak to Jones.
Sinclair was later summoned by Duncan Todd to inform Rodney and Bradley Mitchum that it was Jones who was conspiring against them to keep them from their insurance claim on a hotel they owned that had burned down. He followed this command and showed up at the Silver Mustang Casino, declaring this lie and telling them that they had an enemy in Dougie Jones.
Upon seeing the brothers happily bring Dougie to work, Sinclair fearfully called Todd, who gave him one day to kill Jones. He went to Detective Clark, requesting a poison. However, when the time came to do the deed, Sinclair became near-hysterical and disposed of Jones' poisoned coffee.
He and Dougie went to Mullins' office, where he confessed to his activities with Todd and was asked to testify against him.