Poem on Criminal Mind?

I'm not sure what episode it is when Hotch wive has already past away, while the team searches for a serial killer he's inform he can retire. Hotch sister in law also tells hshe'll help with his son. The finale scene he's sittin at her grave alone & he's goin to stay on with the team, as the show ends he says the poem.....what poem is it? This episode is bout a serial killer that uses his job as a valet to find his victims homes with thier own gps, his upset with burnetts do the fact his would be wife left him & cheated with the best man. I need the poem please.