This Space Between Us contains the opposite of an 11 o’clock number. The nonmusical scene late in the play is a showstopper all right, though not in the rousing good sense. Rather, all action and dialogue literally stop while two characters stand over an air mattress as it inflates. It lasts ... well, however long it takes an air mattress to inflate, which may only be about a minute but seems a lot longer, since the audience has to sit there and wait out this unnecessary moment in a show that has already worn out its welcome.