TEWKSBURY — A $150 drug deal was all it took to blow open a fentanyl trafficking case — and expose an illegal immigrant teen cops say was carrying enough poison to kill thousands.

Police say 18-year-old Dany Mejia Gomez of Lynn, a Honduran national with no right to be in the U.S., walked into a Main Street bathroom expecting easy cash. Instead, undercover detectives swarmed.

The takedown netted 21 grams in the sting itself — then another 121 grams hidden in his Toyota Corolla, along with two iPhones and $1,330 in cash. In all, more than 140 grams of cartel-grade fentanyl were seized, as reported by the Boston Herald.

ICE was called immediately. Agents confirmed Mejia Gomez is in the country illegally and slapped a detainer on him. He’s now locked up without bail in Billerica, facing trafficking charges in Lowell court — and a one-way ticket out of the country.

Massachusetts Democrats may shower illegal immigrants with perks and demonize ICE at every turn. But the moment a trafficker without papers shows up with cartel poison, it’s ICE that gets the call.