Watery Grave - S1.E5

Byder gets some information about the theft of the Stone of Sorrow from a museum. The interest to Ethaniel and Laura is that a guard swears that the two men who stole it carried it out themselves. This would be impossible for humans, as it weighs 3 tons. Banning and Gant are their main suspects, but what would they want with an old relic?