I'm having trouble with my return spell. Any help???

mob
verb
Cast()
var/list/spelllist = new
for (var/O in usr.worldspell)
spelllist += O
spelllist += "Cancel"
var/spellchoice = input("Which spell do you wish to cast?") in spelllist if(spellchoice == "Return")
returnspell()
proc
returnspell(mob/M as mob)
var/list/rettownchoice=new()
var/O
for(O in usr.rettown)
rettownchoice += O
rettownchoice += "Cancel"
var/returnchoice = input("Which town would you like to return to?") in rettownchoice
if(returnchoice == "Ryuzak")
M.Move(28,179,1)
if(returnchoice == "Atlan")
M.Move(49,3,2)
if(returnchoice == "Rubius Castle")
M.Move(68,3,5)
usr << "[returnchoice] = return"


runtime error: Cannot execute null.Move().
proc name: returnspell (/mob/proc/returnspell)
usr: Rubius (/mob/god)
src: Rubius (/mob/god)
call stack:
Rubius (/mob/god): returnspell(null)
Rubius (/mob/god): Cast()