Lock Up is a set of preposterous plot devices cobbled together: Frank Leone (Sylvester Stallone) is sent to prison for taking the law into his own hands when he avenges an attack on his father. Just a week before he is released, he escapes from prison to be at his father's death bed. He then ends up serving five more years for this new crime. The warden of the prison which Leone escaped from, Drumgoole (Donald Sutherland) still bears a grudge against him, since Leone was the only inmate to escape under Drumgoole's tenure. During the last six months of the five year term, Drumgoole has Leone transferred from a minimum security prison to a maximum security prison where Leone is faced with numerous obstacles and has to fight for his freedom. To top it all, just three days before his release, Leone decides to escape again.
It's not unbelievable that Leone could face a whole prison of hostile inmates and a malicious warden and come out on top (Stallone has played characters that have beaten worse odds). What is unbelievable is that a person could be so unlucky and/or stupid.
Donald Sutherland, one of my favourite villains, and actors, is great here as usual, but he is too sophisticated for the role of the warden. Stallone's acting is decent, and he actually has more than a few lines in the movie. Darlanne Fluegel as Leoni's love interest doesn't have much to do. It's better than an average movie, but I'd skip this one unless you have nothing better to do.