NCIS Vance (Rocky Carroll) leads a team assigned to protect a congresswoman (Mary Stuart Masterson) who is the target of threats that appear to be escalating. Mark Harmon, Pauley Perrette, Sean Murray, David McCallum, Emily Wickersham, Wilmer Valderrama and Jennifer Esposito also star. 8 p.m. CBS
The Flash The ongoing threat from Savitar during the holiday season prompts Barry (Grant Gustin) to travel to Earth-3 and consult with Garrick (John Wesley Shipp), while Cisco (Carlos Valdes) reflects on his brother on their first Christmas not shared. 8 p.m. KTLA
The Middle A neighbor (Brooke...