In an all-new episode of "Chicago Fire" titled "The Last One For Mom" airing Tuesday night, Lt. Kelly Severide continues his babysitting duties. However, when the situation takes a turn for the worse, the firefighter is Ieft to deal with the aftermath.

In the upcoming episode, Det. Holloway once again drops off her nine-year-old son JJ at Firehouse 51. While she is apologetic for asking Severide to once again look after her son, she acknowledges that JJ's school homework will be best completed with the help of the firefighters.

During last week's episod,e "I Will Be Walking," JJ showed disinterest in anything related to the firehouse. However, after befriending both Severide and the firehouse dog, he now looks forward to these visits.

Meanwhile, in a sneak peek, Holloway reveals that she is set to testify against the Mexican cartel that she was investigating in the previous episode. However, it seems that the cartel will not back down quietly. Her situation takes an unexpected turn and Severide has no choice but to deal with the aftermath.

Friend and co-worker Lieutenant Matthew Casey will also encounter a bit of trouble in "The Last One For Mom." He receives a suspicious package in the mail that leads to an investigation from the Board of Ethics. Could this recent stunt have anything to do with the recently introduced political consultant Susan Weller?

According to TVLine, Dawson gets a bad feeling about Susan as she is "suspicious of this woman's intentions." However, she will try not to say anything for fear of coming across as a jealous girlfriend.

Firehouse 51 also responds to a fire at an art gallery in "The Last One for Mom." When the firefighters discover that someone is still trapped inside, Cruz decides to rush toward the fire and save the trapped victim. Unfortunately, this rash decision may have deadly consequences for Cruz and the squad.

Also in the episode, Brett becomes frustrated with Otis when he refuses to deal with his health issues and instead focuses on the annual firefighting conference in Las Vegas.

To see how everything unfolds, be sure to catch "The Last One for Mom" airing on Apr. 26.

Season 4 of "Chicago Fire" airs every Tuesday at 10 p.m. ET. on NBC.