Saints slipped to third spot in the Women's Super League table after a 30-14 defeat against fellow title rivals Castleford at the Mend-A-Hose Jungle.
The Tigers took the lead after seven minutes as Tara Stanley went around the outside of the Saints' defence from a clever scrum move.
St Helens battled back and snatched the lead thanks to quickfire tries from Zoe Harris and Leah Burke.
However, it would be Castleford who went into the break ahead. Stanley doubled her account by spotting a gap in the Saints' defence and then two minutes before the break the hosts established a four point advantage when Georgia Roche crashed over the whitewash.
The game was delicately poised on a knife edge until the hour mark when Tigers Rhiannion Marshall threw a sublime dummy from acting half back, fooling three in the process of scoring.
Saints’ afternoon would soon get harder as Chantelle Crowl was sent from the field.
Emma Lumley powered over from the resulting penalty tap before the visitors crossed late on thanks to Tara Jones.
But Cas had the last laugh as Roche jinked her way through the Saints' defence to score her second of the game.