Traveling with Dr. Iris Perez to Iceland to investigate activities attributed to local superstitions, the Alden siblings learn the legend of the mischievous huldufolk elves before uncovering clues that offer scientific insights into the strange phenomena.
"Under Spark Elf's direction, Santa delivers presents in the allotted twenty-four hours only to arrive at the North Pole with a stowaway in the toy bag, a family's beloved dog"--Provided by the publisher.