Miranda is not going to get them out. This leaves Clarke two options: Either wait and see or escape by himself.
Beating his way out would be easy, but Miranda doesn’t like it when he hurts people or breaks things.
So instead he is going to dig a tunnel by the wall in the far corner of the grounds. Dirt is piled high around him when his left hand jams into something hard. Miranda stirs. His control is slipping.
Before she can take over completely, he digs around the hard thing and pulls a long metal box into the light.