EXETER – Firefighters rescued a 16-year-old horse after its hind legs fell through the stall floor in a barn at 137 Linden St. Sunday night. Tim Sirois, crew chief with the Exeter Fire Department, said the department received the call at around 6 p.m. Upon arrival, he said they found the horse named Mulan still upright, but its back half was left suspended straddling a support beam, while its back legs dangled below. With the help of Katherine Dwyer, director of the Rowley, Massachusetts, nonprofit Patriot Equine Technical Rescue, and veterinarian Kirk Smith, of Amesbury (Massachusetts) Veterinary Hospital, firefighters hatched a plan to place loop rescue straps under the 1,600-pound animal, then roll it onto its left side and safely slide it out of the barn while sedated.