Mark O`Brien is a Canadian actor and director who is popular for playing the role of Des Courtney in Republic of Doyle and Tom Rendon in Halt and Catch Fire, and for working in movies like Quiet at Dawn and End of Days, Inc. His other releases include Arrival (2016), The Darkest Minds (2018) and Bad Times At The El Royale (2018). His 2019 release includes Ready Or Not, directed by Matt Bettinelli-Olpin.