Dr Guan Sijia (Fann Wong) is a brilliant lung tumour specialist. Pretty and possessing a pleasant disposition, she naturally has many suitors. But she remains dispassionate towards them, for deep in her heart, she is unable to forget her doctor boyfriend Tang Xinyang (Christopher Lee), who died in a traffic accident.

Before the accident, Xinyang had called Sijia from overseas to say that he has just bought their engagement rings. Sijia had gently berated him for spoiling the surprise. “I’m afraid I won’t have the chance to tell you,” he had replied.

Since his death, Sijia has always appeared calm and composed, but inwardly, she is crippled with agony and yearning. Besides looking after Xinyang’s mother and his autistic younger brother Xinhai (Nick Shen), she puts all her energy into her work.

Working together with Sijia in the hospital are Dr Li Xiaohu, also affectionately called Dr Tiger (Tay Ping Hui), a charming and optimistic person who gets along superbly with everyone in the hospital. His mentor, Dr Liu Zhengyu (Huang Wenyong), is the director of the Communicable Diseases Centre, whose wife Wang Wei (Xiang Yun), is an epidemiologist.

The turning point came when 2 female patients, May and Xiuming, who have just returned from Hong Kong, are admitted to the hospital. Unknown to everyone, the two carry the deadly SARS virus.

Sijia, Xiaohu and their colleagues, which include an internship doctor Xiao Liao (Zhang Yaodong), nurses Xiaoyun (Le Yao), Michelle (Felicia Chin), Daisy, Irene and Zhihao, thus begin their days of ‘war’.

Sacrificing time spent with their family, and risking the danger of contracting SARS, the brave medical heroes battle hardship and discrimination from some members of the public. Although they are mentally and physically worn-out, their fighting spirit is unfaltering.

Amidst this difficult time grows love. Xiao Liao is secretly in love with Sijia, but the young lad is too shy to express his feelings. On the other hand, Xiaoyun is interested in him. She takes the initiative to show her concern for him, but before her love has a chance to blossom, tragedy strikes.

Xiaohu and Sijia develop a strong friendship while on the frontline of defence against the disease. After witnessing the fall of many colleagues to the disease, Xiaohu realises the fragility of life, and thus openly expresses his love for Sijia.

Although Sijia appreciates Xiaohu for his feelings and efforts towards her, she is adamant about remaining loyal to the dead Xinyang. But soon, just when she realises that she has subconsciously fallen in love with Xiaohu, Sijia develops a high fever and is diagnosed with SARS.

Will Sijia and Xiaohu have a happily-ever-after ending, or will Xiaohu be subjected to the same devastation of losing a loved one?  

肺部肿瘤专科医生关斯嘉医术高明，长得漂亮有气质，追求者众，她却都不为所动。原来她有过一段刻骨铭心的爱情。男朋友汤心洋也是个医生，一次意外死在异乡，她从此寄情工作，把对男朋友的思念与爱深埋在心底。

斯嘉表面上虽然平静，心中的悲伤还是不减，除了照顾心洋母亲及患有自闭症的弟弟心海外，就全情投入医务工作。

斯嘉与哥哥斯文同住。关斯文是个保健用品促销经理，高大威猛，却非常怕输怕死，与前妻离婚后，带着儿子与妹妹关斯嘉住在一起，有一个结识两年的导游女朋友杨美娜。杨美娜欣赏关斯文的体贴与爱心，但是受不了他的过度罗嗦与怕输性格，经常因此争吵，是一对欢喜冤家。

杨美娜的父亲杨冲是个蔬菜商，二弟杨伟雄在跨国公司任职，小弟在中学就读，杨伟雄本性自私自我，一向与家人关系较疏离。杨家的蔬菜摊是当年杨冲的父亲留下来的，杨冲的哥哥杨勇一直耿耿于怀，指杨冲霸占父亲的产业，两家人为此常吵闹不休。

某日，斯嘉家隔壁搬来新住客。这个年轻人被经纪欺骗，租了间空荡荡、没水没电的空房子。当晚他敲门要求斯嘉让他的手机充电。斯嘉对这个不修边幅的年轻人没有留下深刻印象。

第二天斯嘉往医院途中遇见一路人晕倒，该名年轻人在场急救，斯嘉才知道他是新来的驻院医生李小虎。李小虎为人风趣，他也是传染病中心主人刘正宇和病毒学家王薇夫妇的学弟，大家都亲切地叫他Dr Tiger。

就在他上班几天后，医院就住进了两个刚从香港旅行回国的女病人，他们都不知道，这两人身上竟带着炸弹似的病毒－SARS！ (Source: Mediacorp Website)