This bill, titled "Grant's Law," amends the Immigration and Nationality Act to significantly expand mandatory detention requirements for certain non-citizens. It specifically mandates that the Secretary of Homeland Security detain any alien determined to be unlawfully present in the United States who is arrested for an offense that would make them inadmissible or deportable. A key provision ensures that detention continues even if the alien is not convicted of the arrested offense, requiring the Secretary to maintain custody until removal proceedings are fully completed. The bill also clarifies that while the Secretary may release the alien to other authorities for criminal proceedings, custody must be resumed when the alien is not under the other authority's control. Finally, it mandates that for these specifically detained aliens, the removal proceedings must be completed within 90 days of their initial detention.