Tiril, Oliver and Ocho head to Moklehoma City in the US with grandpa Franz to investigate the claimed spotting of a real-life unicorn. Cowboys patrol the streets of the town, just like in the old Wild West. The President of the Natural History Society has promised a reward of a million dollar to whoever manages to capture the unicorn. But do unicorns even exist? This is undoubtedly a case for Detective Agency No. 2, who ride out on the prairie to get to the bottom of the mystery. But they’re not the only ones searching for this special animal…

Along the way we get to take part in the solving of the mystery, just like in the other thrilling activity books from the Detective Agency No. 2 universe.