The Strangers on Montagu Street, the third in Karen White’s enchanting series, follows through to “The House on Tradd Street” and “THE LADY on Legare Road.” Psychic realtor Melanie Middleton is still repairing her Charleston home and doesn’t expect to have a new houseguest, a teen lady named Nola. But the young lady didn’t come by itself, as well as the spirits that followed Nola don’t seem willing to keep…