What happens if I can't make a legal move?
The rules cover this on page 13 and 25 when covering Dracula's movement rules

Crossing His Own Trail


  Dracula may only move to a location if its
  card is available to him. Thus, he cannot normally
  move back into a location while its card
  remains in his Trail or Catacombs. The only
  exception to this rule is when he uses his
  Double Back Power card (see “Dracula’s
  Powers,” page 20). In the unlikely event that
  Dracula maneuvers himself into a position
  where he has no legal move, he is punished as
  though he were caught cheating (see
  “Cheating,” on page 25) and then takes his
  turn as normal (assuming he didn’t lose the
  game).


Cheating


  Hopefully, the Dracula player will never cheat
  on purpose. But if he makes a move and later
  finds out that he accidentally moved along a
  rail route or made a similarly illegal move, it’s
  important to undo the damage and get the
  game underway again. However, Dracula also
  needs to suffer a penalty to make up for the
  Hunters’ lost time. We suggest the following
  penalty for a Dracula player who catches himself
  (or is caught) cheating. Although it may
  seem severe, the hope is that the Dracula player
  will quickly learn to be more careful in the
  future.
  
  • Dracula immediately clears his Trail down
  to one card and reveals his current location.
  • Additionally, Dracula loses Blood as
  though he had just suffered a “Killed”
  result in combat. However, if this would
  reduce him to 0 Blood, it only reduces
  him to 1 Blood instead.