I'm playing a Bard in a 5E campaign. One of my most useful spells has been Dissonant Whispers. It's saved the party quite a few times but the question has come up and I've not found any answers in the rules as written for the spell. On a failed save, the creature takes 3D6 psychic damage and the spell causes it "to move as far as its speed allows away from you." However, there's no explanation as to how far it goes or if it ever comes back.
How far and for how long does the target run away?
(At present, we have have house ruled that it is gone for the duration of the battle, but we're considering a dice roll with a minimum of 5 rounds.)