In Pandora And The Mysterious Box answer why did pandora and epimetheus open the box second time

As Pandora and Epimetheus cowered in their cottage and the Troubles spread across the world, they heard another sound – a small voice asking to be let out of the box. It was Hope. And, though they were afraid the two children opened the box a second time and released Hope. Hope had been packed in the box by the Greek Gods to make amends for the swarm of ugly Troubles.
Meaning of cowered= crouch down in fear