Abstract. Its conceivable that there is an undiscovered neutral stable particle made of quarks (uuddss), with mass near twice the proton mass. If so, it could be the dark matter. I will discuss how it can be that such a particle could have gone unnoticed and how to detect it. Remarkably, a particle with these properties can both explain the observed abundance of dark matter at high accuracy, and account for the observed 10-sigma deficit in primordial Li7 compared to the prediction of the standard cosmological model. Even if such a particle does not exist, or exists but is not the dark matter, investigating the problem provides a fascinating tour through modern cosmology and particle physics - which will be presented in a manner accessible to non-experts.