The inside story of the Boston Marathon bombing investigation: Scott Pelley interviews Boston Police Commissioner Ed Davis. Lara Logan gets a rare look into the secretive world of these special dogs, some of whose capabilities are classified. Lesley Stahl gets the first in-depth look at the National September 11 Memorial Museum currently under construction seven stories below ground at ground zero, touring the massive space, getting a preview of its planned exhibits, and speaking to its director, president, and family members of victims who sit on its board.