Nonmonotonic variation with collision energy () of the moments of the net-baryon number distribution in heavy-ion collisions, related to the correlation length and the susceptibilities of the system, is suggested as a signature for the quantum chromodynamics critical point. We report the first evidence of a nonmonotonic variation in the kurtosis times variance of the net-proton number (proxy for net-baryon number) distribution as a function of with significance for head-on (central) gold-on-gold () collisions measured solenoidal tracker at Relativistic Heavy Ion Collider. Data in noncentral collisions and models of heavy-ion collisions without a critical point show a monotonic variation as a function of .