Ben Barba stole the show as his hat-trick of tries handed St Helens a 36-18 victory that saw them advance to the Challenge Cup quarter-finals.
Long-range tries from Regan Grace and Barba handed Saints a 12-0 lead after an even first-half.
But Barba’s second shortly after half-time put the visitors 18-0 ahead, with the fullback also producing some spectacular defensive efforts too.
Jake Trueman and Greg Minkin hit back for Cas, but Ryan Morgan and Danny Richardson restored the lead before Barba’s stunning third try put the game to bed.
Castleford: Shenton; Minikin, Webster, Wardle, Hitchcox; Ellis, McShane; Watts, Milner, Sene-Lefao, Holmes, McMeeken, Foster. Subs: Moors, Millington, Cook, Trueman.
St Helens: Barba; Makinson, Morgan, Percival, Grace; Lomax, Richardson; Amor, Roby, Thompson, Peyroux, Taia, Wilkin. Subs: Fages, McCarthy-Scarsbrook, Douglas, Knowles.