、。。
When I hurried to Grandma's house, the door wasn't locked. So I went inside.
Literal
I [subject-が] grandma [of-の] house [to-に] hurry-[and-て] go-try-[when-と], house [on-には] lock [subject-が] was-not-applied. So I [topic-は] house [of-の] inside [to-に] entered.
A narrative with multiple elements: 急いで (hurrying adverbially) + 行ってみる (try going) + と (upon which) + 錠がかかっていなかった (lock wasn't applied). 錠 is the noun for 'lock' (as a physical device); 錠がかかる = 'a lock is applied' — fixed expression. そこで ('so, therefore') is a narrative connector meaning 'and then, thus.' A classic storytelling chain.