No Neutral Wire

I am trying to install a smart switch (Insteon brand - don't ask... I don't love them but I have no alternative for this location). I am replacing an existing toggle switch and found that the the work box has a hot wire, a load, and a ground - but no neutral. If I connect the neutral wire and the ground wire from the Insteon switch to the existing ground wire in the work box, everything works. I know this isn't up to code, but otherwise, I don't know how to install the smart switch in this work box. How dangerous is this setup? Are there any alternatives? Thanks in advance for your help!