Two agents working for the government must hide a federal witness, Dr. Franz Tobel, who has been  targeted by assassins. They choose a little island 13  miles off the Rhode Island Coast. How they get there, and what  happens to the witness, is told in this exciting new thriller that  brings back characters first introduced in “The Block Island  Mystery Writer’s Retreat.” Hold on tight as storms rage and people are not who they seem to be in “Dangerous Crossing  To Block Island.”