The Hollow ~ Nora Roberts

This is the second book in the Sign of Seven trilogy
This is the story of Layla and Fox, Fox is one of three boys who accidentally let loose a demon on his home town with a blood brother ceremony when he was only ten. The demon attacks his town, every seven years, for seven days. Fox and his blood brothers are soon approaching their 31st birthday, and the fourth occurrence of the attacks.
This time there have been 3 women drawn into town, and through research and odd happenings, they have been drawn into the fight to get rid of the demon. some are unsure if they will survive this occurrence of the Seven, and others are determined to live anyway.

Blood Brothers ~ Nora Roberts

This is the first in the Sign of Seven trilogy. Cal Hawkins and his two best friends went out on a camping trip for their tenth birthday, and inadvertently set something free. What ever it is comes back every 7 years, for 7 nights. Now, as the 3rd return approaches, Quinn wants to write a book about the strange happenings in Hawkins Hollow. She gets to town and starts to investigate, and strange things begin to happen. Will they figure out what they need to do?