Sam could barely hear Buffy's words as his shoulder or even foot couldn't get the door down. How did Dean do it all the time? Sam stepped back, rubbing his shoulder, his leg aching. He tried to think of another way, possibly the bathroom window but then what she said sank in.
She said smoke. And smoke to him could only mean one thing to to him. Demon. A demon was trying to possess her. Immediately Sam started speaking Latin.
"Exorcizamus te, omnis immundus spiritus, omnis satanica potestas, omnis incursio infernalis adversarii, omnis legio, omnis congregatio et secta diabolica, in nomine et virtute Domini Nostri Jesus Christi, eradicare et effugare a Dei Ecclesia, ab animabus ad imaginem Dei conditis ac pretioso divini Agni sanguine redemptis. Non ultra audeas, serpens callidissime, decipere humanum genus, Dei Ecclesiam persequi, ac Dei electos excutere et cribrare sicut triticum. Imperat tibi Deus altissimus, cui in magna tua superbia te similem haberi adhuc præsumis; qui omnes homines vult salvos fieri et ad agnitionem veritaris venire. Imperat tibi Deus Pater; imperat tibi Deus Filius; imperat tibi Deus Spiritus Sanctus ..."
Sam knew the words by heart, especially since he was a kid. He hoped it would work, he had to get her out.