midnight
It is hot , down in the depth of the great Lowland areas , and it is chiefly adventurers and outcasts of human kind who can endure life in what few towns there are . Into Nareda , the capital village of the tiny Lowland Republic of Nareda , goes Philip Grant , an operative of the United States Customs Department , on a dangerous assignment -- to ferret out the men who are smuggling mercury into the United States from that place . Grant falls in love with Jetta , the daughter of Jacob Spawn , a big mercury mine owner of Nareda , only to learn that Spawn has promised her in marriage to Greko Perona , the country 's Minister of Internal Affairs . Grant follows Perona to a midnight Lowland rendezvous with mysterious strangers and eavesdrops on them , sending their indistinct voice murmurs to his chief , Hanley , in Washington , who relays them back to him , amplified . He learns several important things : that Spawn and Perona and a depth bandit named De Boer are together involved in the smuggling ; that they have planned a fake robbery of a fortune in radiumized mercury stored at Spawn 's mine , to collect the insurance on it and escape paying the Government export fee : and that they , plan to kidnap Grant for ransom . The plotters learn of Grant 's absence from Nareda , and suspect that he may be nearby . They start to search for him .