I'm searching for the title of a comic book from the mid-sixties in
the suspense/sci-fi genre. The story involved a prisoner who heard
from a dying inmate of a device which would allow it's user to escape
by digging a tunnel under the prison walls. A sadistic guard allowed
the prisoner to "find" the device (the guard planted it), not
believing it would work, thereby breaking the man's spirit. The
prisoner finds the device, but to the guard's dismay, it functions,
and the prisoner escapes to a sub-terranian world of benevolent
aliens, who had created the device long ago.