That's correct? It's accusative and not "ręce"?
"Ręce" would be Dative or Locative, and not Accusative (as already pointed out). But beware of the declension of "ręka". The noun has some archaic forms which are directly inherited from the ancient Dual (neither Singular nor Plural) number.
1. Ence, pence, w której ręce? (Locative)
2. Mam cię w ręku! (Locative as well!, but originally meant to say "I keep you with my both hands/I can control you on something" (the Dual number form that has survived until today, even if the Dual ceased to exist in Polish some 200 years ago).