'Best friends Frankie and Drew are desperate to win this year’s Halloween costume parade, and they know exactly what will give them the edge: authentic Viking costumes from olden-day Norway!
The plan is simple: use their secret Sonic Suitcase to get in, get helmets, and get out. But they weren’t counting on accidentally bringing back a Viking called Birger with them – plus his angry brother Brynjar, who really has it in for Frankie and Drew. Can the boys round up the vikings, get them back home and win the costume parade before anyone discovers what they’ve done?'
Source: Publisher's blurb.