You can't properly re-heat treat steel unless you know what type of steel it is to start with! Different steels require different hardening & tempering procedures.
What Tozzy is recomending about heating & quenching it could easily ruin the blade. - It would certainly change its properties. Oil quenching is used to give a different chill cooling rate & any carbon migration from the oil into the surface will only be in the very thin outer skin - one touch on a sharpener will remove that.
Casenite is used as a shallow case hardening process & it can get hardness penetration a thou or two, but again not very deep & you would soon cut it away with sharpening.
Deep (say 25 thou) case hardening takes many hours of sustained red heat in a carbon rich environment (carburizing) then quenching to harden the carbon rich surface layer.
To the OP - best option is to grind it to the profile you want on a whetstone with water cooling so it simply doesn't get hot. If you do get it up to the temperature when the bright metal starts to colour, yellow, then brown & blue, the material properties will probably change (depending on material type) & you are getting into the tempering range of temperature & if it is a normal carbon steel blade, you will certainly be softening it. Quenching it at that stage will fix that new softness into the material.
If you cant get onto a whetstone, you can grind it on a free cutting dry stone but extreme care must be taken to avoid it heating at the cutting edge. Grind & cool in water at very regular intervals - just dont get it hot - not even for a second!!
Ian