Holders Halifax fell at the first hurdle of the Northern Rail Cup as they lost 20-18 to Dewsbury at the Tetley's Stadium.
The Rams led for most of the first half, courtesy of a try from Ryan Hepworth and a Bobbie Goulding goal. They had two other tries disallowed by the video referee.
Halifax also had a try by Sam Barlow disallowed before substitute Callum Casey levelled the scores two minutes before half-time and they took a 12-6 lead with Paul Handforth's converted try five minutes into the second half.
The home side regained the advantage thanks to tries from Scott Hales and Tommy Gallagher. Goulding then kicked two penalties to extend his side's lead to eight points and the cushion proved crucial when Halifax hit back with winger Wayne Reittie's late try.