To scheme or plot (often with a secret or malicious intent); to plan or conspire.
彼らは会社を乗っ取る計画をたくらんでいた。
They were scheming to take over the company.
裏で何かをたくらんでいるような怪しい動きがある。
There are suspicious movements as if someone is plotting something behind the scenes.
彼は友人をだますつもりで細工をたくらんだ。
He schemed a trick intending to deceive his friend.