midnight
Now use of the grounds was restricted to affairs of long standing that it would be inconvenient to change or to cancel . That was a definite effect , he admitted to himself . But who could profit by it ? There was only one possible clue , and that lay in the midnight prowlings of the Blue Ghost and his varying number of companions . Turning the picnic area into a forbidding place , a haunted ground , would give the ghost and friends ample opportunity to roam the upper and lower fields without interference . Only , why roam the fields ? Somehow , the radioactive dust in the cement bags must tie into it , but Rick could n't imagine the connection .