A bullied teenage girl forms an unlikely friendship with a mysterious young man who protects her from her assailants, while she copes with the pressures of her final examinations.

上元节前夕，长安城混入可疑人员。身陷囹圄的张小敬临危受命，与少年天才李泌携手务必要在十二时辰内破除隐患。