Olenna Tyrell removes poison vial from Sansas necklace

Clip from Game of Thrones, HBO is the owner of this video material, all rights reserved for HBO...

Olenna Tyrell removes poison vial from Sansa's necklace, the necklace Ser Dontos gave her on espisode 1 from season 4, then it seems Olenna gives the poson vial to Mergaery (barely visible)...