The IceCube Puzzle

Astrophysical neutrinos are unambiguous tracers of hadronic interactions of cosmic rays (CRs) in our Universe. With this in mind, high energy neutrino astronomy has long been anticipated to help uncover the orgin of high energy CRs. The recent detection of a flux of high-energy extra-terrestrial neutrinos by the IceCube Observatory is an important step in this direction. However, the low statistics and angular resolution of the signal makes an identification of the neutrino sources challenging. I will review various scenarios for the IceCube signal, ranging from exotic PeV dark matter decay to the more conventional candiate sources of high energy CRs. I will finally discuss various multi-messenger observations that can help us to solve the IceCube Puzzle.