The House on the Cliff is the second in Franklin W. Dixon’s “Hardy Boys” series, although if you haven’t read the first book in the series, you will still enjoy it.
Frank and Joe Hardy are told by their father, world famous detective Fenton Hardy, that he is working on a top secret case involving smugglers, and that the two boys can help by keeping watch on the ships around Bayport, where the Hardys live.
Using their father’s telescope, Frank, Joe and their friends Chet Morton and Biff Hooper keep watch on the ships around Bayport. When they are on their way home, they spot a boat chasing another one and stop to take a look. When the pursuing boat catches up, the friends see a grenade being threw at the other boat! They rescue the man driving the boat, who had escaped just in time. Shortly after this their father Fenton disappears! Frank and Joe decide to investigate.
Who were the people that threw the grenade and who did they throw it at? More importantly, will Frank and Joe find their father in time?