It is based on 1 Samuel 4:1-18.  In this episode, Samuel is poised to speak, but says nothing.  In fact, he does not even appear in what follows.  Instead, Israel and Philistia square off in battle.  Inexplicably, Israel loses.  Figuring that God had not shown up, the Israelites make sure that God appears by bringing the Ark of God into the next battle.  Israel nevertheless loses again.  Worse, Eli’s two sons are killed and Philistia captures the Ark.