desktop-restore-in-current-display is a variable defined in `desktop.el'.
Its value is

Controls how restoring of frames treats displays.
If t, restores frames into the current display.
If nil, restores frames into their original displays (if possible).
If `delete', deletes frames on other displays instead of restoring them.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.4 of Emacs.