The next time you hit a creature with a melee weapon attack during this spell's duration, your weapon glows with lightning, and the attack deals an extra (2d8) lightning damage to the target.  For the duration of the spell, your weapon forms a connection of lightning between the target.  As long as you remain within 30 ft. of the target, the target takes lightning damage equal to (1d8) plus your spellcasting ability modifier on the start of its turns, and can't take reactions for the duration of the spell.  If you move more than 30 ft. away from the target, the spell ends. 

If there is another enemy within 5 ft. of the original target, the electricity conducts to the other enemy.  This spell can only affect a maximum of two targets.  The second creature must make a Constitution Saving Throw, taking lightning damage equal to (1d8) plus your spellcasting ability modifier on a failed save, or half as much damage on a successful save.  If the spell affects a second creature within 5 ft. of the original target, both creatures take lightning damage at the start of their turns for the duration of the spell. 

At Higher Levels.  When you cast this spell using a 3rd level spell slot of higher, both the spell's initial damage and later increase by (1d8) for each spell slot level above 2nd.