In this comic-book-style talk, I will take you along the adventures of protagonists Spirou and Fantasio as they explore the enigmatic tau Boötis exoplanetary system. Their quest? To study the atmosphere of this keystone hot Jupiter and relate its inferred envelope composition back to our understanding of how giant planets form. In this presentation we will follow our heroes as they use the new high-resolution near-infrared SPIRou spectrograph to observe the dayside of the non-transiting hot Jupiter tau Boo b. With its simultaneous 0.95-2.50um wavelength coverage and R = 70000 spectral resolution, SPIRou delivers an unprecedented sensitivity to both H2O and CO, the primary carbon- and oxygen-bearing molecules expected in hot Jupiter atmospheres. Join me today to find out how Spirou and Fantasio combine a total of 20 hours of SPIRou data obtained over five nights to not only recover a precise CO abundance corresponding to a C/H ratio consistent with the value of Jupiter, but also to retrieve the exact temperature structure of tau Boo b, and infer an extremely depleted water abundance of less than 100 times the expected value for a solar composition. Finally, our adventurers will link these unexpected results to the larger population of giant planets, and how these may form in the protoplanetary disk.