Arc Lightning

As you point at a target within 15 feet, a crackling bolt of lightning springs forth from your outstretched fingertip. The target must make a Dexterity saving throw. A creature takes 3d6 lightning damage on a failed save, or half as much damage on a successful one. Arc lightning may then jump to two additional targets within 5 feet of the each target. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d6 for each slot level above 1st.