[warning: might be offensive]
A messenger of Allah to the children of Israel (exclusively), born of a virgin, had followers from the poor and 12 disciples (the Hawariyyun), the 13th being Judas Iscariot who betrayed him and gave him away to Romans. He did not die on the cross but Allah lifted him to heaven, and he will return in end-times as Imam Mahdi, the leader of the faithful, broke the cross, and converted Christians to Islam.
However, Paul, a former Jew, coopted his teachings and preached to non-Israelites, something that Jesus himself did not do. Later, as a result from the dispute of two theologians, Arius & Athanasius, the Consul of Nicaea declared Jesus as God. And so the trinitarian heresy begins.